Technical Report UMTRI-2004-31
March 2005
Alternative Images for Parallel Parking:
A Usability Test
of a Multi-Camera Parking Assistance System
Sean Michael Walls, Paul Green, Sujata Gadgil,
John Amann, and Brian Cullinane
umtri
HUMAN FACTORS
Technical Report Documentation Page
1. Report No.
3. Recipient’s Catalog No.
2. Government Accession No.
UMTRI-2004-31
4. Title and Subtitle
5. Report Date
Alternative Images for Parallel Parking: A Usability Test
of a Multi-Camera Parking Assistance System
March, 2005
7. Author(s)
8. Performing Organization Report No.
6. Performing Organization Code
account 381577
Sean Michael Walls, Paul Green, Sujata Gadgil,
John Amann, and Brian Cullinane
9. Performing Organization Name and Address
10. Work Unit no. (TRAIS)
The University of Michigan
Transportation Research Institute (UMTRI)
2901 Baxter Rd, Ann Arbor, Michigan 48109-2150 USA
11. Contract or Grant No.
12. Sponsoring Agency Name and Address
13. Type of Report and Period Covered
Nissan Research Center
Nissan Motor Co., Ltd.
1 Natsushima-cho Yokosuka, 237-8523 Japan
6/06-6/05
Contract DRDA 04-0266
14. Sponsoring Agency Code
15. Supplementary Notes
AVM and Low Speed Maneuvers: Human Factors Issues Project
16. Abstract
The parking assistance system evaluated consisted of 4 outward facing cameras
and a center console monitor. Camera image combinations examined included
(1) Front/Back Switching (showing either a forward or rear scene depending on the
direction of travel), (2) Front/Back Combined (showing both images concurrently),
(3) an Aerial View, and (4) an Aerial View combined with a Front/Back image.
Sixteen drivers (8 under age 30, 8 over age 65) parallel parked a 2002 Infiniti Q45
(full size sedan) in a 25-foot long parking space between 2 cars. Each subject parked
and exited 18 times, using the various image combinations or none at all.
The interface with the best performance depended on the measure, and often it was
the case that no assistance at all was the best. The Front/Back Switching interface
had the shortest parking time (56.4 seconds) and the fewest number of maneuvers
(4.1) and the largest margin for error in terms of the closest approach to other
vehicles. However, the interface in which both images were shown simultaneously
(Front/Back Combined) had the smallest mean distance to the curb (7.2 in).
Interestingly, the interface with the fewest number of contacts with other vehicles (2
out of 48 entrances + 48 exits) and the curb (24) was the Aerial view. Except for the
number of maneuvers and parking time, and a few others, the performance measures
were uncorrelated.
Comments indicated problems occurred because subjects were unsure (1) what
was being shown (forward or rear, the camera direction, and what corresponded to the
bumper in the image) and (2) of distance to objects (because images were distorted).
17. Key Words
18. Distribution Statement
Driving Performance, Parking, Accidents,
Crashes, ITS, Human Factors,
Ergonomics, Safety, Usability, Telematics,
Driver Vision, Indirect Vision
No restrictions. This document is
available to the public through the
National Technical Information Service,
Springfield, Virginia 22161
19. Security Classify. (of this report)
20. Security Classify. (of this page)
(None)
(None)
21. No. of pages
22. Price
96
Form DOT F 1700 7 (8-72)
Reproduction of completed page authorized
i
ii
ALTERNATIVE IMAGES FOR PARALLEL PARKING:
A USABILITY TEST OF A MULTI-CAMERA
PARKING ASSISTANCE SYSTEM
UMTRI Technical Report 2004-31
March, 2005
Sean Michael Walls, Paul Green, Sujata
Gadgil, John Amann, and Brian Cullinane
University of Michigan
Transportation Research Institute
Ann Arbor, Michigan
USA
1 Primary Issues
1. How close to the parked vehicles did drivers steer as a function of the parking
assistance system used, driver age and sex (and their interaction), and practice?
2. How close were they to the curb as a function the parking assistance system
used, driver age and sex (and their interaction), and practice?
3. How centrally did the drivers park the car in the parking space?
4. How did parking time vary as a function of the parking assistance system and its
features, driver age and sex (and their interaction), and practice?
5. How did the number of parking maneuvers vary as a function of the parking
assistance system and its features, driver age and sex (and their interaction),
and practice?
6. How did the number of impacts with surrounding vehicles and the curb vary as a
function of the parking assistance system and its features, driver age and sex
(and their interaction), and practice?
7. How well do the various measures of parking relate to each other?
8. How well did drivers rate the different parking assistance system images and the
system overall?
9. What comments did drivers make about the parking assistance system images
and system overall?
2 Methods
Image from
Front of Car
Image From
Back of Car
Switching
Front/Back Switching: Subjects saw either a forward or rear image depending on
the gear selected (forward or reverse). The in-car experimenter switched the images
based on the gear selected, simulating an automatic system.
iii
Front/Back Combined: In this image,
the image components from Front/Back
Switching are presented simultaneously
(no switching) as a single image, and
did not change with the gear selected
(forward or reverse).
Aerial View: This image uses all 4
cameras and a superimposed virtual car
icon to show a 360-degree single view of
the car and is presented as if there was a
camera flying over the car as it moved.
Parking Trial
Sequence:
1) Park 3 times, get
out, and check
clearance
(familiarize in
practice spot)
2) Park 3 times without
assistance
(baseline)
This image combines the front/back as
the left component and the aerial image
as right component of a new image.
This image was meant to present both
general (Aerial) and more specific
(Front/Back Combined) information to
the driver as they parked.
3) Park 12 times (4
images x 3 times
each)
4) Park 3 times without
assistance (baseline
check)
Total = 18 times
Subjects (16 total)
Young (18 - 30)
Old (60+)
iv
Men
4
4
Women
4
4
3
Results and Conclusions
Closest Approach Values By Location
Rear Enter
Front Enter
Front Exit
Rear Exit
Mean
Std
Dev
Mean
Std
Dev
Mean
Std
Dev
Mean
Std
Dev
Beginning
Control
Front/Back
Switching
Front/Back
Combined
Aerial
44.4
10.1
36.5
15.0
28.3
10.2
43.5
8.9
45.7
11.5
38.2
13.2
30.0
7.8
43.6
6.5
43.6
10.4
33.4
12.7
29.6
9.1
43.4
7.3
44.1
11.2
35.8
16.0
29.1
10.7
44.6
8.1
Front/Back/
Aerial
Ending
Control
Overall
44.9
12.1
35.3
14.7
27.7
9.9
43.2
6.8
42.2
9.1
34.7
13.3
28.7
9.8
44.5
7.9
44.2
10.7
35.6
14.1
28.9
9.6
43.8
7.6
Closest Approach By Trial
Tire-To-Curb Distance
v
Front Tire
Rear Tire
- Front / Back Switching Decrease distances by 3%
- Most images increased distance, and images that show the curb the best showed
the largest increase in tire and curb impacts.
Tire-to-Curb Distance Learning Effect
Nearly all of the decrease in distance was due to practice.
Bumper-to-Bumper Distances
vi
Centeredness
Image
(inches)
Std Dev
Beginning Control
11.6 (best)
38.0
Front / Back Switching
20.3
37.0
Front / Back Combined
21.9
40.0
Aerial
17.1
43.3
Front / Back/ Aerial
23.5
38.1
Ending Control
18.3
32.2
A zero value represents a centered vehicle
“Centeredness” = Rear
Bumper to Car Distance
- Front Bumper to Car
Distance
(+) Car is positioned
forward in space (-) Car
is positioned rear in
space
Parking Time and Number of Maneuvers
Mean: 4.2 Std Dev: 2.4
Bi-modal in pairs of maneuvers
Mean: 59 Std Dev: 35
Lognormal (3.95,0.47)
Smallest Mean and Std Dev:
Front / Back Switching
Smallest Mean and Std Dev:
Front / Back Switching
Impacts By Location and Image
Image Component, Time and Maneuver Correlations
vii
viii
TABLE OF CONTENTS
INTRODUCTION ............................................................................................................. 1
TEST PLAN .................................................................................................................... 5
Overview ..................................................................................................................... 5
Participants ................................................................................................................. 6
Camera Images and Virtual Eye Point ........................................................................ 9
Parking Lot and Equipment Set Up ........................................................................... 12
Test Car .................................................................................................................... 17
Sequence of Experimental Tasks.............................................................................. 18
RESULTS ..................................................................................................................... 21
Dependent Measures ................................................................................................ 21
Data Reduction ......................................................................................................... 22
When parking, how close to the parked vehicles did drivers steer? .......................... 23
When subjects were finally parked, how close were they to curb?............................ 29
When subjects were finally parked, how close were they to the stationary
vehicles? ............................................................................................................... 36
How did parking time vary? ....................................................................................... 42
How did the number of parking maneuvers vary? ..................................................... 45
How did the number of impacts with surrounding vehicles and the curb vary? ......... 49
How well do the various performance measures of parking relate to each other? .... 51
How well did subjects rate the different parking assistance system images and
the system overall? ............................................................................................... 52
What did the subjects have to say about the images? .............................................. 53
CONCLUSIONS ............................................................................................................ 55
1. When parking, how close to the parked vehicles did drivers steer? ...................... 55
2. How close to the curb did subjects park? .............................................................. 55
3. How close to the stationary vehicles did subjects park? ....................................... 55
4. How did parking time vary? ................................................................................... 55
5. How did the number of parking maneuvers vary? ................................................. 55
6. How did the number of impacts with surrounding vehicles and the curb vary? ..... 56
7. How well do the various measures of parking relate to each other? ..................... 56
8. How well did drivers rate the different parking assistance system images and
the system overall? ............................................................................................... 56
9. What comments did drivers make about the parking assistance system images
and system overall? .............................................................................................. 56
Closing Thoughts ...................................................................................................... 56
REFERENCES .............................................................................................................. 59
APPENDIX A – SUBJECT CONSENT FORM .............................................................. 61
APPENDIX B – SUBJECT BIOGRAPHICAL FORM.................................................... 63
APPENDIX C – PRETEST SCRIPT .............................................................................. 65
APPENDIX D – PARALLEL PARKING INSTRUCTIONS ............................................ 67
APPENDIX E – POST-EVALUATION FORM ............................................................... 71
APPENDIX F – TESTING EQUIPMENT LIST .............................................................. 73
APPENDIX G – UMTRI EAST LOT LAYOUT .............................................................. 75
ix
APPENDIX H - DRIVER COMMENTS .......................................................................... 77
x
INTRODUCTION
Over the last decade, automotive manufacturers and suppliers have added into motor
vehicles many new intelligent transportation features and systems such as those for
navigation and collision warning. These systems are intended, among other things, to
make driving safer, more convenient, more productive, and more pleasurable.
Parking assistance systems have received less attention. Several manufacturers
(Table 1) have introduced parking assistance systems that utilize ultrasonic sensors or
video cameras. Ultrasonic sensors use visual and/or auditory signals to alert drivers of
objects or situations needing attention. The camera-based systems, whose cameras
are placed outside of the vehicle, use an LCD located on top of the dashboard, in the
center stack, or in the speedometer/tachometer cluster to provide feedback to the
driver.
Table 1: Parking Assistance Systems
Vehicle
(Year, Make, Technology
Manufacturer/
Model) or
(Camera or
Supplier
Aftermarket
Ultrasonic)
Valeo
Aftermarket
Front & Rear
Ultrasonic
Electronic
Aftermarket
Front & Rear
Commerce
Ultrasonic
Sales, Ltd
Buick
2004 Buick
Standard
Rendezvous Rear
Ultrasonic
Daimler
2005
Standard
Chrysler
Chrysler
Rear
300C
Ultrasonic
Aglaia
Aftermarket
Front & Rear
Camera
Toyota
Corolla
(Prototype)
Infiniti
2002 Infiniti
Q45
Optional
Front Corner
&/or Rear
Camera
Standard
Rear
Camera
URL
http://www.valeo.com/gb/activities/sw
itches_systems/park_assist.asp
www.parking-sensor.co.uk
http://www.buick.com/rendezvous/fea
tures/safety/ultrasonicrearparkassist.
html
http://www.chrysler.com/300/features
/exterior_features/park_assist.html?c
ontext=300-featuresexterior_featuresindex&type=modelsub
http://www.aglaiagmbh.de/english/angebot/prototypen/
rueckfahrkamera.html
http://www.toyotaeurope.com/showroom/corolla_verso/
kce_3.html
http://www.infiniti.com/content/0,,cid32769_sctid-32005,00.html
The human factors and crash research data available for these systems are surprisingly
limited. As an initial step in this project, the human factors literature on parking (10
1
studies) was reviewed. In addition, crash files (Michigan Traffic Facts), which included
10,400 parking crashes between 2000-2002, were analyzed. Finally, 6 State Farm
Insurance agents were interviewed regarding parking and low-speed crashes. The
primary conclusions from those 3 sources were summarized in Smith, Green, and
Jacob (2004) as follows:
1. There are very few human factors studies of how people actually park.
2. Much of the literature (10 studies were examined) on parking crashes is outdated
by 20 years or more. This is a concern because the vehicle mix (cars vs. light
trucks and SUVs) has changed, as has the use of the various parking maneuvers
(more parking lots and less parallel parking).
3. Many of the studies involve unique situations (e.g., small towns, the Midwest U.S.)
that may not be representative of the U.S. as a whole.
4. Much of the published data (e.g., for the State of Michigan) is for crashes that
primarily occur on public roads. However, many parking crashes occur on private
property and are not reported.
5. The predominate parking crash (occurring at least half the time) is backing out of a
parking spot into either:
a. Another car that is backing out of an adjacent space, or
b. Another car moving down the parking aisle.
6. There are few day-night differences in crash rates and most crashes occur in the
daytime, when most driving occurs.
7. Parking crashes very rarely involve alcohol or drugs.
Based on these conclusions, Smith, Green, and Jacob (2004) suggested that 1 way to
prevent parking crashes, especially those associated with backing up, would be the
implementation of an assistive device such as a camera-based parking assistance
system.
Based on the problems drivers have parking and other information, Nissan has been
developing a camera-based parking assistance system known as the Around View
Monitor (AVM). The prototype examined utilizes 4 fixed wide field-of-view cameras
placed around the car (1 in the center of the grill, 1 just above the rear license plate, 1
under each of the exterior mirrors on the sides of the vehicle). Each camera has a field
of view of almost 180 degrees, affording some overlap between the fields of view for
each camera. An image-processing unit “stitches” together images from multiple
cameras to provide an even wider field of view and warps the camera output to remove
lens distortions. Images presented to the driver may be either direct (an image
presented directly from the camera) or indirect (an image that is created from
components that are stitched together, i.e. a “virtual image,” usually involving a
viewpoint change, and as noted, 1 or more than 1 image component).
To be able to assess the usefulness and usability of such a system, baseline data was
needed on:
2
1. How well drivers park without video assistance (the minimally acceptable level of
performance)
2. How drivers park in different situations (i.e., parallel, perpendicular, angled)
This information was needed to determine the criteria for which to evaluate the parking
assistance systems. To obtain these 2 sets of information, Cullinane, Smith, and Green
(2004) carried out a field study in Ann Arbor, Michigan. They measured how well 102
cars were parked in perpendicular, angle, and parallel parking spaces. In addition, they
also completed phone interviews with 20 drivers concerning how often they parked and
problems they had parking.
Results from the interviews showed that men and women parked equally often in all
parallel, perpendicular, and angle parking spaces. Younger drivers parallel parked
relatively less often than middle age drivers and perpendicularly parked relatively more
often than middle age drivers. However, the relative distributions were very similar.
Interestingly, 47% of the respondents reported they felt their parking was more accurate
than the rest of the driving population. An equal amount reported they felt as accurate
as the rest of the driving population, and the remaining few admitted they felt less
accurate.
The driver interviews also showed that at least 75% of the parking instances involved
perpendicular parking with significantly fewer parking events in parallel spaces and
much fewer still in angular spaces. In addition, 75% of the reported problems involved
leaving a parking spot.
The field study contains descriptive statistics concerning parking situations ordinarily
encountered by U.S. drivers. For parallel parking, spaces averaged about 24 feet long.
When an excess of space was available, drivers tended to be positioned forward in the
space such that the excess was at the rear of the vehicle. Interestingly, there was no
relationship between the size of the vehicle and the space around it. The distance to
the curb for parallel parking was typically about 4 inches.
For angle parking, the head-in distance was bimodally distributed, with some vehicles
having the nose of the vehicle over the end of the space (a low concrete barrier), and
others falling short. The same was true for perpendicular parking, though the extent
depended on whether a wall or low concrete barrier was present at the end of the
space.
To follow up on these previous reports, 3 experiments were conducted to examine
perpendicular parking (Walls, Amann, Cullinane, Green, Gadgil, and Rubin, 2004) and
parallel parking (this report) with and without camera assistance, and the minimum
clearance desired for parking in general (Green, Gadgil, Walls, Amann, and Cullinane,
2004). Most of the results from the initial experiments have been incorporated into
design guidelines (Rubin and Green, 2005). The purposes of these experiments was to
select a “best” image or type of image for further development and evaluation, gather
ideas for improvements to the interface, and gain insights into how parking studies
should be conducted.
3
Given this general purpose, the following questions were considered:
1. When parking, how close to the parked vehicles did drivers steer as a function of
the parking assistance system used, driver age and sex (and their interaction),
and practice?
2. When subjects finally parked, how close were they to the curb as a function of
the parking assistance system used, driver age and sex (and their interaction),
and practice?
3. When subjects were finally parked, how close were they to the stationary
vehicles behind and in front of them as a function of the parking system used,
driver age and sex (and their interaction), and practice?
4. How did parking time vary as a function of the parking assistance system and its
features, driver age and sex (and their interaction), and practice?
5. How did the number of parking maneuvers vary as a function of the parking
assistance system and its features, driver age and sex (and their interaction),
and practice?
6. How did the number of impacts with surrounding vehicles and the curb vary as a
function of the parking assistance system and its features, driver age and sex
(and their interaction), and practice?
7. How well do the various measures of parking relate to each other?
8. How well did drivers rate the different parking assistance system images and the
system overall?
9. What comments did drivers make about the parking assistance system images
and system overall?
4
TEST PLAN
Overview
This experiment was conducted in a parking lot at The University of Michigan
Transportation Research Institute (UMTRI), between August 31 and September 14,
2004. Data was collected during daylight hours. Collection took place in both cloudy
and clear weather conditions. Interestingly, collecting data under cloudy conditions was
viewed as ideal due to the lack of screen glare and ground shadows created on sunny
days.
The parking space was between 2 parked cars parallel to the traffic aisle (Figure 1).
The length of the parking space was constant across all subjects (at 25 feet long, about
1.5 car lengths), as were the locations of the vehicles in front and back off the test
space. This distance was approximately the mean value reported by Cullinane, Smith,
and Green (2004) and is within the recommended spacing listed in the American
Association of State Highway and Transportation Officials Green Book, 2001, the
accepted road design manual in the United States. Each subject parked 3 times without
a parking assistance system, then 3 times with each of the 4 images, and finally an
additional 3 trials without the system for a total of 18 trials per subject. The beginning
and ending control data provided as basis for assessing practice effects.
Figure 1. Test Site Overview (not to scale)
When entering a parking space, commonly the primary concern is striking adjacent
vehicles with the front bumper, passenger side front fender, and rear bumper, or driving
into the curb. For reasons of safety, this experiment was designed to practically
eliminate forceful impacts with other vehicles by placing protective dense black foam on
all possible contact areas. Therefore, an associated measure, the closest approach for
each of these areas, was captured using overhead cameras. Other cameras also
provided an overview of the entire maneuver, recorded the subject’s face and torso,
their interaction with the system, and the images presented by the parking assistance
system.
5
Participants
Sixteen licensed drivers (8 young (18-30) and 8 old (over 60)) voluntarily participated in
this experiment, and were paid for their time. The entire experiment lasted
approximately 120 minutes. Within each age group there were an equal number of men
and women. The ages of the younger subjects ranged from 19 to 27 with a mean of 23
years. The older subjects were aged between 61 and 77 years, with a mean age of 69
years.
Seven of the 8 subjects over the age of 60 were retired and 1 was a patient companion
at the Veterans Hospital in Ann Arbor MI. All of the 8 younger subjects were students,
with one, who was not familiar with the study, being a research assistant in a Human
Factors Division of UMTRI.
Four of the 8 younger subjects were new to UMTRI experiments, and 7 of the 8 older
subjects had participated in several studies in the past. On average, these subjects had
participated in 3 previous UMTRI experiments, and 4 had some experience (either
driving or non-driving) with the test car in use. Only 4 subjects reported having driven
with an in-car parking camera.
To determine how representative the subjects were to the driving population, each was
measured for height, weight, and seated eye position within the test vehicle. These
measurements appear in Table 2. The values shown are reasonably typical of adults in
the U.S.
Table 2. Anthropometric Data
Weight
Height
Vertical Seated
Eye Height
Horizontal Seated
Eye Height
Device
Continental Health-OMeter Model 230 kg
210 cm Siber Hegner & Co
standing anthropometer
210 cm Siber Hegner & Co
standing anthropometer
210 cm Siber Hegner & Co
standing anthropometer
Mean
69.7 kg
Range
49 – 100 kg
171.8 cm
155.3 – 189.5 cm
118.9 cm
112.6 – 123 cm
88.2 cm
78.7 – 99 cm
For the seated eye height, the horizontal coordinate originated from the interior driver’s
side door bracket that was located 593 mm on the horizontal (longitudinal) axis from the
center of the front wheel (which is the origin for all measurements during
manufacturing), and the vertical coordinate originated from the road surface. As shown
in Figure 2, there was a slight correlation between the two measurements with taller
drivers sitting farther aft.
6
Seated Eye Height (cm)
124
122
120
R2 = 0.013
118
y = 0.056x + 114.0
116
114
112
70
75 80 85 90 95 100 105 110
Seated Eye Postion Horizontal (cm)
Figure 2. Subject Seated Eye Height Positions
In addition, the subjects’ vision was checked for acuity using the Landolt Ring eye test
on a Stereo Optical Optec 2000 vision tester on the Far #2 setting without a lens and
then again with an 80cm lens. All 16 subjects had normal or corrected vision. Subjects
with normal vision had a far vision between 20/18 and 20/13 and a near vision between
20/20 and 20/18. The subjects with corrected vision had either glasses (11 subjects) or
contacts (2 subjects), and their far vision ranged from 20/100 to 20/17 and near vision
ranged from 20/100 to 20/20.
The 16 subjects on average drove 13,200 miles per year with a range of 600 to 30,000
miles per year. This value is close to the U.S. mean of 10,000 miles/year. Table 3
provides means for parking frequency of the 16 subjects. Table 4 shows the
corresponding values that were found in Cullinane, Smith, and Green (2004).
Interestingly, the percentage of each type of parking varies greatly, although the order
of frequency, and weekday-weekend percentages remain similar.
Table 3. Mean and Percentage Parking Occurrences per Month for Parallel Study
Weekdays
Weekends
Total
Parallel
Perpendicular
Angular
Total
5 (13%)
3 (8 %)
21%
10 (26%)
6 (15%)
41%
10 (26%)
5 (13%)
39%
65%
36%
Table 4. Mean and Percentage Parking Occurrences per Month
From Cullinane, Smith, and Green (2004)
Weekdays
Weekends
Total
Parallel
Perpendicular
Angular
Total
4 (4%)
2 (2%)
6%
54 (59%)
24 (26%)
85%
4 (4%)
4 (4%)
8%
67%
32%
7
Of all 16 subjects, 3 had experienced a parking-related crash within the past 5 years.
Of those 3, 2 subjects had experienced 2 crashes and 1 subject had experienced a
single crash. Three subjects reported experiencing at least 1 non-parking crash within
the last 5 years. Of these 3, 2 subjects reported 1 crash and 1 subject reported 2
crashes. Comparatively, in Cullinane, Smith and Green (2004), the 30 subjects
reported a total of 8 crashes, all of which occurred during parking maneuvers.
The subject’s personal vehicle’s age ranged from brand new to 21 years old with a
mean of 8 years. Ten of the 16 subject’s vehicles were cars. The remaining vehicles
were 2 SUV’s, 3 minivans and 1 truck. Four subjects reported having driven with an incar parking camera. Of these 4, 2 had previously participated in the perpendicular
parking experiment (Walls, Amann, Cullinane, Green, Gadgil, and Rubin, 2004), which
used the same parking assistance system as this study.
To get a sense of subject aggressiveness/risk acceptance, drivers were asked where
they would drive on an expressway with 3 lanes on each side of a barrier. Eight
subjects reported that they usually drive in the center lane. Of the remaining subjects, 5
stated that they normally drive in the left lane and 3 stated they normally drive in the
right lane. Overall, the sample is close to being average in terms of risk acceptance
(where lane choice is not biased left or right).
8
Camera Images and Virtual Eye Point
A total of 4 images (Table 5) were displayed 3 times each to the test subjects during the
parking task. Each image contains at least 1 label (e.g., front, back, right) to aid in
recognition.
Table 5. Images and Descriptions
Image
Description
Subjects saw either a forward (top
image in column on left) or rear
image (bottom image) depending on
the gear selected (forward or
reverse). The in-car experimenter
switched the images based on the
gear selected, simulating an
automatic system.
1- Front And Back Switching
Name
This forward view (top image) shows
the front bumper of the test vehicle
(bottom of the image), and a
substantial amount of the horizon.
The rear bumper of the parked car in
front (another Q45) is at the top of
the image.
The rear view image shows the rear
bumper of the test vehicle (bottom of
the image) and the front bumper of
the car parked behind it (Ford
Taurus). There is slightly less
horizon than the front image.
2- Front and Back
Combined
In this image, the image components
from image 1 are presented
simultaneously (no switching) as a
single image, and did not change
with the gear selected (forward or
reverse).
Again, the top image was provided
by the front camera and the bottom
image was provided the rear camera.
9
3- Aerial
This “Aerial View” image uses all 4
cameras and a superimposed virtual
car icon to show a 360-degree single
view of the car and is presented as if
there was a camera flying over the
car as it moved. When passing close
to other vehicles (one of which is
shown in the bottom section of this
image) those other vehicles appear
distorted in the vertical plane. This is
due to the low angle of the image
required to produce the aerial effect.
4- Front/ Back/ Aerial
This image combines the front/back
image (image 2, which itself contains
2 image components) as the left
component and the Aerial image
(image 3) as right component of a
new image. In the Front/Back image,
the test vehicle’s bumpers are
located at the bottom of each
respective component image. The
Aerial image is again distorted as
mentioned above. This image was
meant to present both general
(Aerial) and more specific
(Front/Back Combined) information
to the driver as they parked.
According to Shepard and Metzler (1971) and related literature, the time to make samedifferent judgments concerning pairs of images (in this case the image on a monitor and
an internal reference) depends on the angular difference (e.g. in degrees) of the
orientation of the 2 images as well as a factor that considers the number of dimensions
over which translation and/or rotation must occur.
A key consideration affecting image selection for parking assistance was where the
optimal “virtual viewpoint” should be located. The virtual viewpoint is the apparent
location of the camera, developed by warping the image or images from the original
physical location or locations.
The virtual and actual viewpoints could be identical (if the camera was near the driver’s
eyes and aimed in the same direction). Figure 3 provides some example options for the
forward scene indicating changes in camera pitch angle and translation path relative to
the vehicle. There are an infinite number of possibilities. For the sake of simplicity, only
2 paths in the YZ plane were examined.
10
Im age 3, 4-right
component
Im ages 1, 2,
4-left component
Z
-X
+X
Y
Figure 3. “Virtual Eye” Viewpoint
The first, vertical path would be one straight up in the +Z direction from the driver’s
location. This path results in the rotation of the camera as the virtual eye is translated
up along the path. A second curved path in addition moves in the –Y direction, thus
adding a second translation to the image. Each of the candidate image components fits
on 1 of the 2 paths (or a related path rotated 90 degrees on the XY plane). On the
previous basis, the images on the curved path should be more difficult to use than those
on the vertical path, as when they are interpreted they will require a translation and a
rotation, as opposed to only a rotation on the vertical path.
Ultimate image development needs to balance the effort required for the driver to
translate their viewpoint into that of the image, with how well the image shows the scene
to be judged. For example, in situations where horizontal distances are important, and
elevated vertical perspective directly above the front bumper clearly shows the gap
between the front bumper and forward obstacles. However, this requires drivers to in
some sense “imagine” what they might see from a helicopter flying very low over the
bumper; a rather abstract concept. In contrast, the direct upward translation requires
less imagination (it resembles being in a very tall seat) but does not show the gap as
well because the virtual eye viewpoint is not directly above the gap.
The 4 images were chosen to allow the best location of the “virtual-eye” viewpoint to be
examined in a somewhat systematic manner. Other key variables including zoom and
its affect on the field of view, and image quality, was partially confounded with eye point
location, and accordingly were not examined given the limited resources available.
11
Parking Lot and Equipment Set Up
Subjects completed the experiment in portions of the east parking lot at UMTRI in Ann
Arbor, MI. The layout of the east lot is shown in Appendix G.
A line of 5 parallel parking spaces, each measuring 25 feet long, was used during the
course of the experiment. From front to back, the spaces were, (1) the car parked in
front of the test space, (2) the space in which parallel parking occurred, (3) the car
behind the test space, (4) buffer space, and (5) a space to practice parallel parking.
As was seen in Figure 1, driving performance was recorded using four video cameras
mounted above the test vehicle. Table 6 lists the locations and cameras used as well
as the height of each camera over the ground.
Table 6. Camera Locations and Heights
Location
(above)
Front Corner
Front Bumper
Curb
Rear Bumper
Overview
Camera / Lens
SuperCircuits PC165c CML2-10MMZ
SuperCircuits PC165c CML2-10MMZ
SuperCircuits PC165c CML2-10MMZ
SuperCircuits PC165c CML2-10MMZ
SuperCircuits PC197, 3-8mm built in lens
Height
(Ft in)
8 9-1/2
8 8-1/2
7 2-1/4
7 2-1/4
15 0
As shown in Table 7, the 2 front cameras were mounted to 8-foot long 2 x 4 inch
wooden booms and attached in the middle to a Bogen Model #3061 tripod, which stood
on the rear end of an Infiniti Q45. The curb camera was mounted to an 8-foot long 2 x 4
inch wooden boom and clamped to a Werner folding ladder. The rear center camera
was mounted to an 8-foot long 2 x 4 inch wooden boom and attached in the middle to a
Bogen Model #3061 tripod, which was placed on the front end of a Ford Taurus station
wagon. An overview camera was positioned to the side of the parallel parking space
and mounted to a light pole. All cameras were high enough such that they were out of
the field of the subjects and could not be used to guide the test vehicle into the test
space.
12
Table 7. Camera Apparatus and Setup
Rear-Camera Apparatus
The rear bumper camera was mounted
to a ¼ inch plywood slat, with 2 x 4
inch protective blocks on either side
(removed for picture) as seen below.
This slat is attached to the 2 x 4 boom,
which is fixed to the tripod stand as
shown below.
13
Front-Bumper, Front-Corner Dual Apparatus
Each camera was mounted to a 2 x 4
inch block, which was attached to its
respective 2 x 4 inch boom. The
booms were attached to each other
using nuts and bolts, and the dual
boom system was mounted a single
tripod
Curb Apparatus
This camera was mounted on a 2 x 4
inch block, which was attached to a 2 x
4 inch plank, serving as a boom. This
boom was then fixed to a ladder using
C-clamps, as shown below.
14
Pole-Mounted Apparatus
This camera was mounted a 2 x 4 inch
block, which was fixed to a lighting pole
centered next to the test space. This
camera was mounted much higher than
the others to afford an overall view of the
test area. The camera feed was sent into
and RF transmitter (box below camera),
and received at the test vehicle’s A/V
Rack.
This camera was used solely to monitor
the entire testing space.
A dedicated VCR individually recorded the video feed from each of the parking space
cameras. The locations, and the types of equipment that recorded each feed is listed in
Appendix F.
During testing, there were 2 experimenters. One was in the test vehicle to interact with
the subject, serve as a safety observer, operate the in-car video equipment, and verify
the trial. The second experimenter, on-foot, was in charge of overseeing the majority of
the video recording equipment (primarily for the parking space cameras). The video
recording equipment was on a cart located under a tent to prevent sunlight washout of
the monitors, and overheating of the equipment. This tent also provided shade to the
on-foot experimenter. In addition, the on-foot experimenter used the tire-to-curb
measuring device, which is shown in Table 8.
15
Table 8. Tire-to--Curb Distance-Measuring Device
Consisting of a sliding metal ruler
mounted flush to a wooden block, the
apparatus, when placed next to the curb,
aligned the ruler with the center of the
wheel. To assure accurate placement, a
steel angle bracket (mounted on the
base plate pointed downwards) was
butted into the gap between the curb
and the grass.
A view down the measuring device
showing the alignment of the ruler with
the center axis of the wheel. Distances
were read from the outside of the curb
(see above), and a correction factor (the
curb width) was later subtracted to
reduce the distance to the actual
distance between the tire and the curb’s
vertical face.
A view from overhead of the device
showing how the apparatus was
positioned and how the values were
read after each trial (here 12 in, before
correction).
Both the front and rear tire distances
were recorded for each trial.
16
Test Car
Subjects completed the experiment using a black, instrumented 2002 Infinity Q45. Per
the sponsor’s specifications, an 8-inch diagonal LCD monitor was mounted to the top of
the front dashboard to display the test images. A proprietary 6–button control device,
used to change images, was mounted into the existing control console as shown in
Figure 4.
8-inch Panasonic TR8LWV4 LCD monitor.
Infinity Navigation
System LCD Screen
was covered during
testing to prevent driver
distraction from the
parking assist system.
Proprietary 6-button
control device.
Location of test subject
Audio Technica AT803b
mic.
Figure 4. Q45 Center Console Layout
Inside the car, 2 identical microphones recorded dialogue between the experimenter
and the subject. One microphone was located under the 6-button control device and
the other was mounted to the in-car instrument rack. In addition, there were 2 cameras
to record the subject and interaction with the parking assistance system.
The in-car electronics stack, operated by the in-car experimenter, can be seen in
Figure 5. An equipment list can be found in Appendix F.
17
Figure 5. In-Car Electronics Stack (Looking left from the right rear passenger seat)
Nissan developed the camera-based parking assistance system. The in-car electronics
were powered with dual AC-DC and DC-AC Converters to ensure a clean power supply.
All proprietary image-processing hardware along with a Dell Latitude D505 was stored
in the trunk. As mentioned previously, the software could manipulate each of the
signals from the 4 cameras (located on the front and rear bumpers and the 2 side
mirrors) and present a single image to the driver, or an image with multiple components.
Based on interaction with UMTRI, Nissan programmed the software for the image
processor. Images could be changed using the keyboard and a 10.5-inch monitor from
the back seat, or by using the proprietary control device from the front seat.
Sequence of Experimental Tasks
The experiment lasted approximately 120 minutes and followed the sequence in
Table 9. When subjects arrived, they were escorted into the UMTRI building. The
subject signed a consent form (Appendix A) and completed a biographical form
(Appendix B). The experimenter followed a predetermined script (Appendix C).
18
Table 9. Procedure and Descriptions
Step Task
Description
1
Biographical forms
2
Introduction to car
3
Introduction and
explanation
4
Vehicle Familiarization
5
Parking protocol (Trials
1-3: Control Trials)
Parking protocol (Trials
4-15: With System)
Parking protocol (Trials
16-18: Control Trials)
Post-experiment
evaluation
Forms were completed with information
such as name, gender, height, weight,
type of car usually driven, parking
patterns, car crashes, and an eye exam.
Showed subject how to adjust the seat
and mirrors. Measured seated eye
position: horizontal and vertical.
Briefly described the experiment to the
subject including the general task to be
completed.
parked 3
in a parking spot with no
times
cars in front, or behind.
Each time, the subject got
out of the vehicle to check
final position spacing.
parked 3
without assistance from the
times
system
parked 3 x 3 times with each of four
4 times
different image combinations
parked 3
without assistance from the
times
system
Subject filled out forms rating each
individual images and the camera
assisted parking system as a whole.
6
7
8
Approx.
Time
(min)
15
5
5
10
15
45
15
10
After step 1, the subject proceeded to the car and adjusted the driver’s seat to a
comfortable driving position. The subject’s seated eye position was then measured.
The subject then adjusted the mirrors and the in-car experimenters got into the car to
begin the next phase of the experiment. The subject was told the purpose of the
experiment was to determine if pictures from TV cameras mounted on the car could
help with parking. Subjects were told to keep the car running at all times to avoid
problems with the camera system. To become familiar with the test vehicle, subjects
looped around the parking lot and parallel parked in a practice spot (designated by lines
on the road surface with no cars near it) three times. Each time the subject parked,
they got out of the car and looked where they parked to see how close the car actually
was to the space markers and curb.
While this occurred, the on-foot experimenter started the VCRs recording the stationary
cameras of the test space. Next, a checkerboard grid of 1-inch squares was placed in
the field of view of each camera at a designated height for calibration.
19
Once both the in-car and on-foot experimenters and the subject were ready, the on-foot
experimenter held up a clipboard displaying the subject, image and trial numbers. The
in-car experimenter verified these numbers, and walkie-talkies were used to resolve
potential errors. Upon verification, the subject was instructed to drive in a clockwise
loop around the parking lot. As the subject was looping, the on-foot experimenter held
up the clipboard to display the subject, image, and trial number to each camera. This
set of numbers would be used when the tapes were analyzed to label trials for the tape
reviewers.
As the subject completed the loop, the in-car experimenter instructed them to park to in
the designated spot on their right between the parked (stationary) Q45 and Taurus.
When the subject was satisfied with their position in the parking space, they put the
gearshift into park and waited for instruction to drive the loop again.
Subjects were allowed to reposition the test vehicle as many times as necessary to
obtain satisfactory parking. In many cases, the subject chose to pull completely out of
the test space, re-align the vehicle with the forward stationary car, and re-attempt the
maneuver from the start. Consequently the number of parking maneuvers per image
trial was also recorded. After the maneuver, the number of test vehicle / stationary
vehicle and test vehicle / curb impacts were recorded by the in-vehicle experimenter.
After the in-car experimenter verified the next trial number with the on-foot experimenter
(to make sure each image was shown the desired number of times in the predetermined random order), the subject pulled out of the space, looped around the
parking lot, and parked again.
After the subject parked for the third control trial, the in-car experimenter started the DV
recorder and while the car was in park, the first image was displayed for the subject to
interpret. Subjects were encouraged to use the images to help them park when safe to
do so. Experimenters engaged the subject in dialog about each of the images to
determine which areas of the image were helpful, and what comments the subject had
regarding the image, the system, or what they were seeing on the LCD screen.
There were a total of 18 trials; 3 beginning control trials without the cameras, 12 trials
with the cameras (4 images, each shown 3 times in a row), and then 3 additional ending
control trials to check for learning. The presentation order of images was
counterbalanced across subjects.
When the 18 trials were believed completed, the on-foot back experimenter verified this
was so using the image check sheet, and by communicating with the in-car
experimenter. The subject then filled out the post-experiment evaluation form
(Appendix E) rating each image as it was displayed on the screen and answered
questions about the usefulness of the system as a whole. At the conclusion of the
survey, the subject was paid $40.
20
RESULTS
Dependent Measures
As previously mentioned, cameras were mounted above (1) the rear of the car in front,
(2) the front of the car in the rear, and (3) the curb to capture the closest approach
distance for each parking maneuver. A separate VCR recorded the output of each
camera and the tapes were reduced after data collection was complete. The areas of
interest are indicated below in Figure 6.
Figure 6. Areas of Interest During Entering and Exiting Parking Space
To begin the parallel parking task, the subject would position the test vehicle next to the
forward stationary vehicle, and place the car into reverse. The area of “Rear Corner
21
Entry” is the minimum distance that occurred between the test vehicle’s rear passenger
corner, and the forward stationary vehicle’s rear driver corner as the test vehicle backed
into the parking space. As the test vehicle continued backing into the space, the driver
would turn the wheel to “swing” the front end around into the spot. The area of “Front
Corner Entry” was the minimum distance that occurred between the test vehicle’s front
passenger corner, and the forward stationary vehicle’s rear driver corner. Once in the
final position, the areas of “Front Bumper” and “Rear Bumper” were recorded on the
video. At the conclusion of each trial the on-foot experimenter easured the passenger
side tire-to-curb distances using the device described earlier.
To assist in determining the closest point of approach from the videotapes during
reduction, a transparency of polar coordinate graph paper was placed on the face of a
monitor, with the origin of the polar system at the point of interest for each location. The
experimenter manually advanced the VCR, watching how many rings from the origin
were between the stationary and moving vehicles. When the minimum was observed,
the frame was frozen and a plastic ruler was placed on the viewing monitor to measure
the distance of interest perpendicular from the front or back bumpers and front corner.
To overcome lens distortion and link the on-screen distance with actual distance, a
correction factor was determined by superimposing a ruler on the screen and measuring
the separation of one-inch squares on a calibration grid that had been videotaped
during each experimental sequence separately for each camera. The distance
measured on screen during the approach was multiplied by the correction factor to
determine the actual closest approach.
Additionally, the final distance from the passenger side tires to the curb was measured
at the conclusion of each trial. Once the subject had placed the test vehicle into park
(indicating that they were satisfied with the parking), the on-foot experimenter measured
the distance from the curb to the outside wall of both tires using the device described
earlier.
Data Reduction
Due to time constraints, 2 analysts working in parallel reduced the videotape data.
Each analyst was responsible for his own locations, and they did not review the other’s
tapes. All approach values were entered into a common data sheet. Limited checks of
the data in which 2 analysts coded the same tape showed the coding was extremely
reliable, with correlations on the order of 0.98, 0.99.
Depending on the number of maneuvers each subject needed to complete the task,
there may have been numerous values for the closest approach at the corners,
however, there was only 1 value for the tire-to-curb distances and the front and rear
bumper distances. Only the final values for the closest approach were analyzed. The
total time of a parallel parking attempt was determined by looking at the overhead
camera footage found on the in-vehicle camera recording (transmitted via RF from the
camera on the light pole and recorded in the test vehicle). To find the total time, the
analyst would reset the VCR clock to 0 when the subject shifted the test vehicle from
the parked position into reverse (seen from torso camera). Once the vehicle was
shifted into park at the end of each parking attempt, the VCR was paused, and the time
22
on the VCR clock was recorded. Any time spent stopped during a trial was recorded as
the idle time. Idle time invariably occurred as a result of a subject-experimenter
discussion or explanation of the interface being tested. After all the time data was
reduced, the idle time was subtracted from the total time to give the total time spent
parking. The total number of maneuvers was found by counting the number of times
the vehicle shifted into reverse or drive, and included instances where the driver backed
in, found they could not repositioned the vehicle easily, and then pulled out to start
again. The first maneuver began when the vehicle was put into reverse to start each
trial and the last was the maneuver that occurred prior to the final park. Hence, backing
up and then pulling forward would be 2 maneuvers. If they backed in and then pulled
out to start again, that also would be counted as 2 maneuvers.
When parking, how close to the parked vehicles did drivers steer?
When entering and leaving a parking space, drivers should not hit other parked
vehicles. The areas of the test vehicle that were most likely to collide with stationary
vehicle were the passenger side corners. Figures 7 through 10 show the overall
distributions for the 4 measures of closest approach (as described in Figure 6) with
means and standard deviations listed for each. All distributions appear to be normal
with values of approximately 44 inches for the rear corner for both entry and exit, and 36
inches for the front corner on entry, and 29 inches on exit. The larger value at the front
for exit makes sense as subjects are only looking forward when exiting, as opposed to
looking both forward and back when entering, and therefore are more aware of the
space.
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
Figure 7. Rear Corner Entering Closest Approach Values (inches)
23
44.2
10.9
0.7
45.5
42.8
250
84.1
19.7
Although the field of view for each parking space camera was set such that no subject
would be out of sight when entering or leaving a parking space (hence there should be
288 observations for each location), there were a few cases where the subject swung
much wider than expected and out of camera view. As it is impossible to cover all areas
with camera coverage, in those extreme cases, the value was treating as missing rather
than being equal to the largest value measurable. As a result, the means and standard
deviations shown are slight underestimates of the actual values. Additionally, there are
only 272 total observations for exiting maneuvers because after the final control trial,
subjects did not exit the space again (i.e., after trial 16, the car was placed in park, and
did not exit the space). It is also important to note that a minimum value of .9 inches
was observed for the front entering clearance. This indicates that while pulling into the
parking space, at least 1 subject had a near impact with the corner of the test vehicle.
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
35.7
14.3
0.8
37.3
34.0
288
79.3
0.9
Figure 8. Front Corner Entering Closest Approach Values (inches)
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
Figure 9. Front Corner Exiting Closest Approach Values (inches)
24
28.9
9.7
0.6
30.1
27.8
272
50
4.8
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
43.8
7.6
0.5
44.7
42.9
272
62.2
23.7
Figure 10. Rear Corner Exiting Closest Approach Values (inches)
With regard to differences between systems, Table 10 shows the closest approach
distances for each control and image, with the smallest mean for each location shown in
bold and the smallest standard deviation in italics. There were no practical differences
between images for each location in terms of the mean distances, with ranges of 3.5
inches for the rear enter dimension, 4.8 inches for the front enter dimension, 2.3 inches
for the front exit dimension, and 1.8 inches for the rear exit dimension. An ANOVA was
performed for each location. It was found that aside from an Age x Sex and Subject
[Age, Sex] effects, no other factors were significant in effecting the closest approach
distances between the vehicles.
Table 10. Mean Closest Approach Distance (inches) by Location and Image
Rear Enter
Front Enter
Mean
Std
Dev
Mean
Std
Dev
Beginning Control
44.4
10.2
36.5
Front/Back Switching
45.7
11.6
Front/Back Combined
43.6
Aerial
Front Exit
Rear Exit
Mean
Std
Dev
Mean
Std
Dev
15.2
28.3
10.4
43.5
8.9
38.2
13.3
30.0
7.9
43.6
6.6
10.5
33.4
12.8
29.6
9.2
43.4
7.4
44.1
11.4
35.8
16.2
29.1
10.8
44.6
8.1
Front/Back/Aerial
44.9
12.2
35.3
14.9
27.7
10.0
43.2
6.9
Ending Control
42.2
9.3
34.7
13.4
28.7
9.9
44.5
8.0
Overall
44.2
10.8
35.6
14.3
28.9
9.7
43.8
7.6
25
But what are the traits of a good system? It should:
1. Minimize the mean approach distance between vehicles (to support maneuvering
in close quarters)
2. Minimize the probability of contacting another vehicle (the ratio of the mean
divided by the standard deviation).
Thus, a good system would have a small mean and a large mean / SD. Table 11 shows
those data, with the mean being the mean of the 4 clearances of interest (front entry,
front exit, rear entry, rear exit).
Table 11. Mean Closest Approach Distance Percentages by Image
% Different
from
Mean Beginning
Control
Mean
% Different
Std
Dev
Mean
Std Dev
Control
Mean
Std Dev
Beginning Control
38.2
0.0
11.01
3.5
0.0
Front/Back Switching
39.4
3.1
9.8
4.0
16.9
Front/Back Combined
37.5
-1.8
9.9
3.8
9.9
Aerial
38.4
0.6
11.5
3.3
-3.3
Front/Back/Aerial
37.8
-1.0
10.9
3.5
0.5
Ending Control
37.5
-1.7
10.0
3.7
8.3
Overall Mean
38.1
-0.1
10.5
3.6
5.1
These data reflect favorably on the front/back switching and the front/back combined
images, mainly because those 2 interfaces reduce the variability of distance between
vehicles (as is evident from the large mean / standard deviation values). When
compared to the overall mean, subjects cleared the stationary vehicles by slightly more
with the Front/Back Switching and slightly less with the Front/Back Combined. When
compared to the other images, as indicate by the percentage difference in the Mean /
SD ratio, the Front/Back Switching and Front/Back Combined were expected to be less
likely to contact the vehicles.
The most noticeable difference between the switching and combined interfaces is that in
the switching interface, only a single image component was presented on the screen at
a time. As a result, the image was larger making distance judgments easier. However,
because the images switched, the subjects may have needed more time to think about
what the image represented and that may have provided an opportunity for error.
The findings regarding the Front/Back images need to be put into context. Changes
from the practice alone (the ending control data) caused subjects to park 1.7% closer
and resulted in a Mean / SD ratio that was 8.3% less than the baseline. However, had
those trials been conducted at the midpoint of the experiment instead of the end and
26
improvements in performance been linear with practice, subjects were expected to park
0.9% closer (approximately 1.7/2) and be 4.2% (approximately 8.3/2) less likely to
contact another vehicle.
Figure 11 shows the mean values of the closest approach distances by trial. Keep in
mind that the image trials were counterbalanced, and that every 3 trials the image was
changed. Overall, the values are stable except for a sharp drop in image trial 6 of the
Front Entry values. The low value reflects an unusually large decrease in approach
distance by 9 of the 18 subjects. For that particular trial, 9 subjects decreased their
closest approach distance by at least 10 inches, and only 3 subjects increased their
distance. The authors cannot explain why this occurred. It should also be noted that
the overall mean values for Rear Enter and Rear Leave are very similar at 44.2 and
43.8 inches respectively, while the differences between Front values are greater (7
inches on average).
Figure 11. Mean Corner Approach Distances (inches) by Trial
Figures 12 through 15 show the Driver Age x Sex interactions for the Front and Rear
Entry and Exit distances. Generally, the young men has the smallest clearances and
the old men the largest, resulting in a commonly reported Age x Sex interaction. As is
typically the case, young men started out with smaller mean values than young females,
but as men age, the values became larger while female mean values became smaller,
though the values for older women were often less than those for young women. The
largest change is seen in the front corner entry with older men’s values being on
average 12.7 inches larger than young men, and with older women’s values being on
average 10 inches less than young females.
27
Figure 12. Age and Sex Differences for Rear Corner Entry Distance
Figure 13. Age and Sex Differences for Front Corner Entry Distance
28
Figure 14. Age and Sex Differences for Front Corner Exit Distance
Figure 15. Age and Sex Differences for Rear Corner Exit Distance
When subjects were finally parked, how close were they to curb?
When attempting to parallel park on a typical street, one of the driver’s goals is to park
as close to the curb as possible. In many cities, parking too far from the curb may result
in a fine. As shown in Figures 16 and 17, the distance to the curb was about 7 inches
on average, somewhat more than the 4 inches reported by Cullinane, Smith, and Green
(2004). The rear wheel was about an inch farther from the curb than the front on a
consistent basis. Overall, the tire-to-curb distances clearly follow a lognormal
distribution. Notice that in a few cases drivers parked almost 2 feet from the curb, a
distance that could lead to a parking fine.
29
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
LogNormal(1.69,0.72)
6.8
4.3
0.3
7.3
6.3
288
22.5
0.5
Figure 16. Front Tire-to-Curb Distance Distribution (inches)
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
LogNormal(1.83,0.75)
7.9
5.2
0.3
8.5
7.3
288
25
0.5
Figure 17. Rear Tire-to-Curb Distance Distribution (inches)
Table 12 shows the front tire-to-curb distances by interface type. Of the interfaces
evaluated, the Front/Back Combined and Aerial images had the smallest front tire-tocurb distance and the Front/Back Switching image had the smallest rear tire-to-curb
distance. As before, the most appropriate practice-adjusted value is the mean value of
the beginning and end control trials. These values are about 7.3 inches (=(8.0 + 6.6)/2)
from the curb in the front and 7.9 (=(6.7 + 9.0)/2) inches from the curb in the rear with
percentage changes of 0.4 and 8.7 respectively. All of the interfaces lead to subjects
parking slightly closer to the curb, with smaller standard deviations. There were very
small differences between interfaces examined, especially given that the accuracy of
tire location measurement was within 1/4 inch. In terms of performance, the interface
that resulted in the largest percentage difference for the control mean / standard
deviation value was the Front/Back Switching image. Given this value, the Front/Back
30
Switching image appeared to be the only image that was beneficial. Surprisingly using
this measure, the aerial interfaces led to worse performance than the mean control.
Table 12. Front Tire-to-Curb Mean Values and Standard Deviations
Interface
% Different
from
Mean Beginning
Control
Mean
% Different
Std
Dev
Mean
Std Dev
Control
Mean
Std Dev
Beginning Control
8.0
0.0
4.4
1.8
0.0
Front/Back Switching
6.9
-13.8
3.9
1.8
-2.7
Front/Back Combined
6.6
-17.5
4.1
1.6
-11.5
Aerial
6.6
-17.5
4.5
1.5
-19.3
Front/Back/Aerial
6.9
-13.8
5.1
1.4
-25.6
Ending Control
6.6
-17.5
3.6
1.8
0.8
Overall Mean
6.9
-13.8
4.4
1.6
-13.8
Table 13 shows how far subjects put the rear tire from the curb when parked. The
values to use for comparing interfaces are -12.8 (-25.6 / 2) for the means and -8.7
(-17.3 / 2) for the mean / SD. Again, differences between interfaces were small, with no
interface decreasing parking distance much more than would be expected with practice
(12.8%). Also as before, subjects were relatively more likely (based on the mean / SD
ratio) to strike the curb using any image than no image at all. The only exception to this
is the Front/Back switching image, which improved performance by 3.0 %. Several
images (the Aerial in particular) were much worse (-23.1%) than the decrease in
performance noted with practice (8.7 %). It is noteworthy that the images that provided
the best view of the curb (Aerial, Front/Back/Aerial) led to the most probability of
contacts (as discussed later).
31
Table 13. Rear Tire-to-Curb Mean Values and Standard Deviations
Interfaces
% Different
from
Mean Beginning
Control
Mean
% Different
Std
Dev
Mean
Std Dev
Control
Mean
Std Dev
Beginning Control
9.0
0.0
5.0
1.8
0.0
Front/Back Switching
7.6
-15.6
4.1
1.9
3.0
Front/Back Combined
7.7
-14.4
4.9
1.6
-12.7
Aerial
8.3
-7.8
6
1.4
-23.1
Front/Back/Aerial
8.3
-7.8
6.3
1.3
-26.8
Ending Control
6.7
-25.6
4.5
1.5
-17.3
Overall Mean
9.0
0.0
5.0
1.8
0.0
How close to the curb drivers parked decreased with practice as shown in Figure 18,
even though subjects had 3 practice trials before the beginning control trials. Tire-tocurb distance through the experiment declined, in particular over the ending control
trials. What does not make sense is why the tire-to-curb distance increased in trials 4,
5, and 6 (trials for the second image subjects used) especially since the order of
presented interface was counterbalanced across subjects. Furthermore, these data
suggest that a considerable amount of practice is required (relative to what can be
accomplished in a single experimental session) before subjects stop improving to a
measurable degree.
32
Figure 18. Mean Tire-to-Curb Distance by Trial
To more clearly differentiate interfaces, Table 14 shows the combined front and rear
tire-to-curb distances for each image used to park (mean of Tables 12 and 13). Given
the desire is to park the car parallel to the curb, one would expect the front and rear
distances to be correlated. This is the case with both for the front and rear mean pairs
(r=0.89) for each interface and the mean / SD pairs (r=0.97) (using the means by
interface).
Examining the combined data, subjects parked an average of 1.8 inches closer to the
curb at the end of the experiment. The values used for comparing interfaces are the
average value of the mean and standard deviation for all control trials. They are -10.8=
(-21.5 / 2) for means and approximately –4.1=(-8.2 / 2) for mean / SD. On average for
each image, (all of which followed the beginning control trial), subjects parked closer to
the curb than without the image. Most of the interfaces are quite close to the expected
improvement that would be expected with practice (10.8%). Of those examined, the
Front/Back interfaces led subjects to park closest to the curb. It may be that drivers do
so well in parking near the curb that there is little room for improvement. Another
possibility is that the system did not provide high-resolution images of the curb and the
area near it, so in the absence of addition visual cues, there should be minimal
improvement. A third possible reason is that the parallel parking maneuver by its pure
nature inherently places the car near the curb (because of the limited maneuvering
space).
33
Table 14. Combined Tire-to-Curb Mean Values and Standard Deviations
Interfaces
% Different
from
Mean Beginning
Control
Mean
% Different
Std
Dev
Mean
Std Dev
Control
Mean
Std Dev
Beginning Control
8.5
0.0
4.7
1.8
0.0
Front/Back Switching
7.3
-14.7
4.0
1.8
0.1
Front/Back Combined
7.2
-16.0
4.5
1.6
-12.1
Aerial
7.5
-12.6
5.3
1.4
-21.2
Front/Back/Aerial
7.6
-10.8
5.7
1.3
-26.2
Ending Control
6.7
-21.5
4.1
1.7
-8.2
Overall Mean
8.0
-6.9
4.7
1.7
-6.9
When the data is examined for an Age x Sex interaction on tire-to-curb distances,
atypical results appear. On average older subjects park closer to the curb, while
younger subjects park further away (6 inches versus 7.5 inches respectively for the front
tire, and 6.75 inches versus 9.1 inches respectively for the rear tire). Although there is
an Age x Sex effect for the front tire-to-curb distance (Figure 19), that effect is not
present in the rear tire-to-curb distance (Figure 20). These data can be see in Figures
19 and 20.
Figure 19. Age and Sex Differences for Front Tire-to-Curb Distance
34
Figure 20. Age and Sex Differences for Rear Tire-to-Curb Distance
An ANOVA was performed twice to determine significant factors affecting the tire-tocurb distances. Included in the analysis were Interface, Age, Sex, Age x Sex,
Subject[Age x Sex] and either overall Trial numbers or Block number. The results
indicated that aside from the Age (p < 0.0008), Subject [Age, Sex] (p < 0.0001), and
Block effects (p < 0.0005), none of the factors examined has a statistically significant
effect on the front or rear tire-to-curb distances.
35
When subjects were finally parked, how close were they to the stationary
vehicles?
Distances were determined by reducing data from the front and rear bumper cameras
separately. Except for 47 trials (29 out of camera view, 18 missing due to a bad tape) all
values were reduced directly from the tapes. For the 47 trials, the missing distances
were estimated by subtracting the front value from 142 inches (142 inches = space size
– car length). After preliminary reduction, all but 95 of the trials summed to within 1 inch
of the maneuvering space. The tapes for those 95 trials were reviewed again and the
distances were re-measured and adjusted to be within tolerance for all but 9 of the
trials. The larger error for the remaining 9 trials was the result of lens distortion from the
cameras used to capture the peripheral elements position data.
A parking assistance system should allow the driver to position their vehicle near the
middle of a parallel parking space’s length. Figure 21 shows the mean distances
between the test vehicle and the front stationary vehicle, and the test vehicle and the
rear stationary vehicle for all trials. These values were 61.5 and 80.3 inches respectively
indicating that the vehicle was positioned forward in the space with 18.8 inches of
additional clearance in the rear. In contrast, Cullinane, Smith, and Green (2004) found
the bias was 7.7 inches to the rear for their sample of parallel-parked vehicles in Ann
Arbor where spaces were slightly larger (291 inches long). They also found that the
front-rear bias was -8.718 + .004 * (space length in inches). Based on these findings a
25-foot space (300 inches) parking space should have a predicted bias of -7.518 or
about -7.5 inches in the rear, close to the overall mean. Overall, drivers tend to position
themselves forward in the parking space, leaving the excess maneuvering space in the
back (194 of 288 or 67% of the trials). The rear bumper to front stationary vehicle
distances can be seen in Figure 22.
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
Figure 21. Front Bumper to Front Stationary Car Distances (inches)
36
61.5
18.9
1.1
63.7
59.4
288
103
0
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
80.3
19.3
1.1
82.5
78.1
288
142
23.3
Figure 22. Rear Bumper to Front Stationary Car Distances (inches)
To determine which image helped subjects park the best with regards to vehicle-tovehicle distances, a measure of “centeredness” was examined for each image.
Calculated from the forward distance subtracted from the rear distance, positive values
indicated that the vehicle was positioned forward in the space, and negative values
indicated that vehicles were positioned towards the rear of the space. A value of 0
represented parking with an even distance ahead and behind the vehicle.
Centeredness did not increase with practice. Rather, it decreased almost linearly for
the first 3 control trials, and then gradually increased for the remaining trials. A plot of
centeredness by overall trial is seen in Figure 23.
Figure 23. Centeredness (inches) by trial
37
Histograms of these centeredness values for each interface appear in Figures 24
through 29. The variability when parking with the Front / Back / Aerial Image was much
less than for other interfaces, though the vehicle was most centered in the beginning
control trials.
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
11.6
38.0
5.5
22.6
0.5
48
114
-52
Figure 24. Centeredness for Beginning Control (inches)
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
Figure 25. Centeredness for Front / Back Switching (inches)
38
20.3
37.0
5.3
31.1
6.0
48
95
-80
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
21.9
40.0
5.8
33.5
10.3
48
142
-62
Figure 26. Centeredness for Front / Back Combined (inches)
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
17.1
43.3
6.2
29.7
4.6
48
130
-75
Figure 27. Centeredness for Aerial (inches)
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
Figure 28. Centeredness for Front / Back / Aerial (inches)
39
23.5
38.1
5.5
34.6
12.5
48
122
-41
Mean
Std Dev
Std Err Mean
upper 95% Mean
lower 95% Mean
N
Max
Min
18.3
32.2
4.6
27.7
9.0
48
99
-36
Figure 29. Centeredness for Ending Control (inches)
When the centeredness data is examined for an Age x Sex interaction, opposite
reactions are seen for men and women. Younger men and women typically park about
20 inches and 16 inches forward in the parking space. As subject age increases,
centeredness values diverge. Compared to young men, older men position the vehicle
further back in the space, while older women position the vehicle further forward in the
space. When examining the centeredness based on age and sex, older men park
closest to the center of the space while older females park furthest from the center of
the space. Again it is observed that regardless of age and sex, subjects typically
position the vehicle forward in the space. These results are consistent with the findings
of Cullinane, Smith, and Green (2004). The Age x Sex interaction of centeredness can
be seen in Figure 30.
40
Figure 30. Age-Sex Interaction on Centeredness
An ANOVA was performed twice to determine significant factors affecting the
centeredness. Included in the analysis were Interface, Age, Sex, Age x Sex,
Subject[Age x Sex] and either overall Trial numbers or Block number. The results
indicated that aside from the Age x Sex (p < 0.0001), Sex (p < 0.0002), and Subject
[Age, Sex] (p < 0.0001), interactions, there were no significant factors in either test
affecting the centeredness of the vehicle.
41
How did parking time vary?
A parking assistance system that is easy to use should minimize the time to park. For
all trials, the mean time was 59 seconds with a standard deviation of 35 seconds.
Figure 31 shows the distribution of parking time appears to be lognormal (3.95,0.47).
Figure 31: Frequency of Parking Times (sec)
As shown in Table 15, there were substantial differences due to practice, with parking
time decreasing by 10.7% (21.3 / 2) and the contact measure (Mean / SD) increasing by
11.3%. In contrast, only the Front/Back Switching interface led to any reduction in
parking time over the control conditions (3.8%), whereas all other interfaces increased
parking time.
Table 15. Parking Time (seconds) by Interface
Mean
58.6
% Different from
Beginning
Control Mean
0.0
Std Dev
33.7
Front/Back Switching
56.4
-3.8
26.3
Front/Back Combined
62.3
6.3
31.1
Aerial
61.5
4.9
28.7
Front/Back/Aerial
68.3
16.6
48.9
Ending Control
46.1
-21.3
34.2
Overall Mean
58.9
0.5
35.0
Interface
Beginning Control
42
How might the differences in parking time between images be explained? Figure 32
shows the relationship between the number of components in the image and parking
time. Notice that it is fairly linear, accounting for 90% of the variance even though it
only contains 5 data points. Each component adds about 5 seconds (about 10%) to the
parking time.
Figure 32. Image Components vs. Parking Time
Interestingly, even though the Front/Back Switching and Aerial images contain only 1
image component each, because the Aerial view is more complex and displayed as a
smaller image on the center console it takes more time to park than the Front/Back
Switching. An examination of image size and its affect on parking was out of the scope
of this study, but this equation suggests that cutting the image size in half adds 5.9
seconds seconds to parking time (62.3-59.4).
As shown in Figure 33, the mean parking time does not change with practice, except for
an increase on trial 4, the first trial with an image system (probably a novelty effect), and
a decrease for trials 16-18, the second set of control trials. Except for those trials,
parking times remain consistent at approximately 1 minute.
43
Figure 33. Mean Parking Time by Trial
As is commonly the case, older drivers took longer to complete the task than younger
drivers, with mean times of 66.8 seconds for older drivers and 50.9 seconds for younger
drivers, a difference of 24% (Figure 34). Interestingly, women consistently took longer
to park than men (68.7 seconds vs. 49.1 seconds). Unlike typical observations, there
was no indication of an Age x Sex interaction on the mean parking time.
An ANOVA was performed twice to determine significant factors affecting the time to
park. As before, included in the analysis were Interface, Age, Sex, Age x Sex,
Subject[Age x Sex] and either overall Trial numbers or Block number. The results
indicated that aside from Age (p < 0.0001), Sex (p < 0.0001) and Subject (p < 0.0002),
there were no factors in either analysis that significantly affected the time to park.
44
Figure 34. Age-Sex Interaction on Parking Time
How did the number of parking maneuvers vary?
Figure 35 shows the distribution of the number of parking maneuvers for all parking
trials. The distribution is bi-modal with a mean of 4.2 and a standard deviation of 2.4.
This bimodality is attributed to the way people park. Typically, parallel parking
maneuvers occur in pairs (a reversal, and subsequent shift into drive). For example,
after the initial 2 maneuvers, if the subject backs up again, there is some probability that
they will need to pull forward again. This observation seems to be true for the first 2
pairs of maneuvers. After that point, subjects made small corrections that did not occur
in pairs.
45
Figure 35. Histogram of Mean Number of Maneuvers
As shown in Table 16, the number of maneuvers to park was reduced from 4.2 at the
beginning of the experiment to 3.6 at the end, or 3.9 at the midpoint. All of the
interfaces required more maneuvers than this control average, though not that many
more considering the level of practice with each image. Of the images, the Front/Back
Switching required the fewest maneuvers.
Table 16. Number of Maneuvers by Interface
Mean
% Difference
from Mean
Std Dev
Beginning Control
4.2
0.0
3.0
Front/Back Switching
4.1
-2.4
1.8
Front/Back Combined
4.5
7.1
2.1
Aerial
4.2
0.0
2.3
Front/Back/Aerial
4.8
14.3
2.9
Ending Control
3.6
-14.3
2.2
Overall Mean
4.2
0.0
2.4
Interface
Again, when the numbers of components are compared to the number of maneuvers as
was done with parking time. A similar but slightly stronger correlation is seen (as the
parking time is directly related to the number of maneuvers) as shown in Figure 36.
46
Figure 36. Correlation between Number of Image Components and Maneuvers
As shown in Figure 37, the number of maneuver data is somewhat difficult to explain.
There is a sharp increase in the number of maneuvers associated with the first trial with
the image systems, then a sharp decrease (which cannot be explained), and then a
steady increase in the number of maneuvers (also, which cannot be explained).
Figure 37. Maneuvers by Overall Trial
Figure 38 shows the Age x Sex interaction on the number of maneuvers performed by
drivers. In brief, older and younger drivers performed roughly the same number of
maneuvers (4.2 vs. 4.3 respectively), though the order due to gender in each age group
47
was reversed, with values being least for young men, and most for old men at 3.3 and
4.5 maneuvers respectively.
An ANOVA was performed twice to determine significant factors affecting the number of
maneuvers. As before, included in the analysis were Interface, Age, Sex, Age x Sex,
Subject[Age x Sex] and either overall Trial numbers or Block number. The results
indicated that aside from the Age x Sex interaction (p < 0.0001), there were no
examined factors in either analysis that significantly affected the number of parking
maneuvers.
Figure 38. Age-Sex Interaction on Number of Maneuvers
48
How did the number of impacts with surrounding vehicles and the curb vary?
During the course of the experiment, the number of impacts between the test vehicle
and the adjacent objects were recorded. These objects included the rear bumper of the
forward stationary car, the front bumper of the rear stationary car, and curb by the front
and rear passenger side tires. Table 17 shows each subject and the impacts with the
vehicle in front, the vehicle to the rear, and the curb.
Given the admonitions of the instructors, there were no hard hits and no damage to the
other vehicles, but a moderate number of “kisses” and a few maneuvers that bordered
on “pushes” (in an attempt to enlarge the test space). Subjects were not adverse to
striking the curb and removing some of the rubber from the tires. Keep in mind that
each subject parked 18 times, though there were multiple opportunities in each
maneuver for subjects to contact other vehicles. Given there were 49 contacts, 288
parking entries (18 trials x 16 subjects), and 272 parking exits, there was a contact on
average for every 11.4 parking sequences (an entry or exit). Contacts in the rear were
6 times more likely than contacts in the front. What is particularly noteworthy is that the
older men were responsible for half of the total contacts in the rear. Finally, worth
noting was that by subject, the number of impacts (front + rear) was highly correlated
with the number of curb contacts (r=0.94), suggesting a generalized parking capability
within individuals.
Table 17. Total Contacts By Subject and Location
Subject
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Total
Age
Sex
Men
Young
Women
Men
Old
Women
Front
Rear
Curb
Total
0
0
0
0
0
2
0
0
0
0
0
0
0
0
5
0
0
3
0
0
2
0
0
8
8
5
6
2
0
0
0
8
11
16
1
11
3
26
10
10
8
8
21
27
7
13
28
4
11
19
1
11
5
28
10
18
16
13
27
29
7
13
33
12
7
42
204
253
49
Figure 39 shows the number of contacts grouped by interface. With practice there was
essentially no change in the number of vehicle or curb contacts, and hardly any
differences between images in terms of the number of contacts except for the Aerial
Image, which had fewer contacts (especially vehicle contacts at only 2).
Figure 39. Location Impacts by Image
As shown in Figure 40, the number of impacts (especially the total), was not consistent
over practice, dipping for trials 6, 7, and 8; trials of two different images each of which
was different across drivers because of the counterbalancing of images. There is no
explanation for this difference.
50
Figure 40. Number of Impacts by Trial
An ANOVA was performed twice to determine significant factors affecting the number of
impacts. As before, included in the analysis were Interface, Age, Sex, Age x Sex,
Subject[Age x Sex] and either overall Trial numbers or Block number. The results
indicated that the only factor that was significant was the Subject [Age, Sex]
(p < 0.0001).
How well do the various performance measures of parking relate to each other?
Table 18 shows many of the performance measures of interest, grouped by interface.
For each measure, the camera-based interface with the best performance is in bold. Of
the interfaces evaluated, there was not a clear “best” Image. The Front/Back Switching
image has the greatest margin of error on the closest approach and distance to the
curb, the least parking time and the fewest maneuvers. The Front/Back Combined
interfaces had the smallest distance to the curb. The Aerial view had the fewest
number of vehicle and curb impacts.
Table 18. Summary of Performance Measures
Interface
Beginning
Control
Front/Back
Switching
Closest
Approach
Mean
Mean
SD
Distance
To Curb
Mean
Mean
SD
Centeredness
Parking
Time
Number
Maneuvers
Mean
Mean
Mean
Vehicle
Total
Curb
Total
Impacts
38.2
3.5
8.5
1.8
11.6
58.6
4.2
10
32
39.4
4
7.3
1.8
20.3
56.4
4.1
8
33
51
Front/Back
Combined
Aerial
Front/Back/
Aerial
Ending
Control
37.5
3.8
7.2
1.6
21.9
62.3
4.5
12
32
38.4
3.3
7.5
1.4
17.1
61.5
4.2
2
24
37.8
3.5
7.6
1.3
23.5
68.3
4.8
7
37
37.5
3.7
6.7
1.6
18.3
46.1
3.6
8
37
Of all of the measures in this table, only 2 were significantly correlated, mean parking
time with mean number of maneuvers (r=0.97, p-.0002). Figure 41 shows that
relationship, with the mean parking time increasing about 17 seconds for each
additional maneuver over the limited range examined. Other correlations of interest
were the closest distance mean/sd with curb mean/sd (the closest approach margin of
error with the curb margin of error) and the closest distance mean/sd with total vehicle
contacts (approach margin of error with vehicle contacts). This is important because
the number of contacts were few and it was hypothesized the margin of error would
predict them.
Figure 41. Time vs. Maneuvers Effect
The absence of correlations could be because the data were highly variable, the
differences were small, or the measures were indeed independent.
How well did subjects rate the different parking assistance system images and
the system overall?
At the conclusion of the experiment, subjects rated the usefulness of each image on a
1-10 scale (10=best). The Aerial image received the highest mean score, had the
highest max, the highest min, and the smallest standard deviation. The rankings are
summarized in Table 19.
52
Table 19. Subjective Image Ratings (1=not useful and 10=most useful)
Interface
Mean
Max
Min
Std Dev
Front/Back Switching
5.7
10
1
2.5
Front/Back Combined
6.9
10
1
2.3
Aerial
7.0
10
4
2.0
Front/Back/Aerial
6.6
10
1
2.7
Subjects were also rated the system overall (1=worst, 10=best), and how comfortable
the system made them feel about parking (1=Very Uncomfortable, 10=Very
Comfortable). As shown in Table 20, overall they thought the system did a fairly good
job at improving their parking ability and making them more comfortable about parking.
It is unclear if they truly felt this way or they were responding to please the
experimenter.
Table 20. Subjective Rating of System and Overall Comfort
Rating
Mean
Max
Min
Std Dev
Overall
7.7
10
6
1.4
Comfort
7.6
10
5
1.4
Finally, subjects were asked questions about the system in general (Table 21). They
were asked if system made them feel safer, and if they used it as a supplement or an
alternative to mirrors. Additionally, they were asked if they felt it took more or less time
to park with the system.
Table 21. Subjective System Qualities
Question
Did the system make you feel safer?
Number of Subjects
Yes
13
No
3
Did you use the system as an
alterative to mirrors, or as a
supplement?
Do you feel it took more or less time to
park with the system than without the
system?
Alternate
7
Supplement
9
More
7
Less
9
What did the subjects have to say about the images?
Subject comments were wide ranging. (For the full list of comments see Appendix H.)
For example, in terms of general comments one subject said using the cameras “took a
lot more nerve” while others said they “made it a lot less stressful.” With regard to the
Front/Back Switching interfaces there were comments about (1) not understanding
generally what was being shown, especially where the camera was aimed (“Ok, now
53
where are we on this?” “Is that us?”, “What is this here?”), and (2) not being able to
relate the image to distance because of distortion (“Now, I can't tell how close I am to
the car behind me”, “Now, how can I tell?”, “I feel like I'm right on top of that car. But
look at how far, look how far it looks away.”)
For the Front/Back Combined image the comments were similar as one would expect,
(1) generally not understanding what was being shown (“Like I said, I don't find this
thing I'm looking at,” “This image is so totally foreign to me it is not helping me”) and
(2) not being able to judge distance due to distortion (“Cause I'm trying to calibrate my
eyes to the image or the reality of the situation.”)
For the Aerial interface, again there were (1) problems of understanding the perspective
shown (“Well, here I am, is this me? I can't…This is back?”), and (2) difficulties with
distortion (“It's still a little tricky judging the distance to the back”) but several subjects
said “I love it!”
For the Aerial Combined interfaces, again, the same types of comments reoccurred,
(1) a general misunderstanding about what was shown/camera direction (“I can't tell
where I am and what's the curb”) and (2) distance distortion (“I'm further away from the
curb, but the image shows me I'm right on top of the curb.”)
54
CONCLUSIONS
1. When parking, how close to the parked vehicles did drivers steer?
On average, clearances were 36 and 44 inches for the front and rear corners on entry,
and 29 and 44 inches on exit. Change with practice (beginning versus end control) of
the 4 clearance values were small, ranging from increase of 1 inch to a decrease of 2
inches, depending on the location. There were hardly any differences between
interfaces in terms of how close subjects steered to parked vehicles, though the margin
of error (mean/standard deviation) was slight larger for the front/back switching interface
than the other interfaces.
2. How close to the curb did subjects park?
Subjects parked on average 8 inches from the curb, a value that is larger than is
reported in the literature and was reported in a field study as part of this project.
Distance to the curb steadily declined with practice. There were no differences between
interfaces in terms of parking distance, though both aerial interfaces provided a much
larger margin for error than the front/back interfaces and the control condition
3. How close to the stationary vehicles did subjects park?
On average, subjects parked 61.5 inches from the front vehicle, and 80.3 inches from
the rear vehicle. These 2 values resulted in a mean centeredness rating of 22.5
indicating that the vehicle tended to be positioned forward in the space. No practice
effect was observed for centeredness. Control trials excluded, the Aerial image had the
smallest mean centeredness value indicating that amongst the interfaces it allowed
drivers to position the vehicle more centered within the space. The smallest mean
centeredness value of 11.6 occurred during the beginning control trials.
4. How did parking time vary?
In this experiment, parking times by interface ranged from 46 to 68 seconds, with a
mean time of 59 seconds, just under 1 minute. In terms of the control conditions, mean
times for the control condition ranged from 59 seconds at the beginning of the
experiment to 46 seconds at the end, a reduction of about 20% (or a mean reduction of
10%). Only the Front/Back Switching interface led to any reduction in parking time
(4%). Most increased parking time. Surprisingly, there were not strong indications of
improvement with practice within each interface, though it could be there were just too
few trials. There was a clear indication that parking time increased linearly with the
number of image components (approximately 5 seconds per component).
5. How did the number of parking maneuvers vary?
The number of parking maneuvers varied from 1 to 18 with a mean of 4.2. The mean
number of maneuvers changed from 4.2 at the beginning to 3.6 at the end, with two of
the interfaces having means of 4.5 and 4.8. In fact, all of the interfaces examined
required at least as many maneuvers as the initial control conditions except for the
55
Front/Back Switching interface, where there was a slight reduction in the number of
maneuvers required (by 2%). There was a very strong linear relationship between the
number of maneuvers when parking and the number of image components, with each
component leading to an additional 3.9 maneuvers. Interestingly, when no components
were present (baseline condition, an estimated 3.9 maneuvers were required, indicating
an average of 2 parking attempts to park the car. The number of maneuvers did not
change in any systematic way with practice.
6. How did the number of impacts with surrounding vehicles and the curb vary?
The number of impacts varied from 0 to 8 per subject and 2 to 12 per interfaces, with 8
for the Front/Back Switching, 12 for the Front/Back Combined, 2 for the Aerial, and 7 for
the Aerial Combined. Thus, in contrast to the number of maneuver and task time data,
the impact data reflect favorable on the Aerial interface.
7. How well do the various measures of parking relate to each other?
The number of maneuvers and parking time (r=0.97) were highly correlated there was
no relationship between the measures of interest. It was expected that the margin of
error (mean/sd) would be correlated with the number of contacts. In addition 2 of the
margin of error measures were correlated with each other and 1 was correlated with the
number of contacts (all r=.60). This is important because there were few contacts and
the margin of error is reasonably easy to obtain over trials.
8. How well did drivers rate the different parking assistance system images and
the system overall?
From best to worst, they ratings were (7.0=Aerial, 6.9=Front/Back Combined, 6.6=Aerial
Front/Back, 5.7=Front/Back Switching. There were no indications that a particular
interface was preferred.
9. What comments did drivers make about the parking assistance system images
and system overall?
Subjects’ comments were often negative and concerned (1) problems of generally
understanding what was being shown, in particular the direction of view, and (2) not
being able to judge distances. There were some positive comments (“I love this
system”) but they were far outnumbered by negative comments.
In contrast to the comments, ratings of the interfaces varied from 5.7 to 7.0 (where
1=worst, 10=best) 7.6 for comfort, and 7.7 for overall. Even though the experimenters
had no part in the physical development of the system, it may be that the subjects
believed that the experimenters had developed the system and did not want to hurt the
experimenter’s feelings by giving a low rating to the systems.
Closing Thoughts
56
This study showed that none of the interfaces were as effective as no image system
(the control condition). That may not be the case if additional labeling was provided on
images to make clear what was being shown. This includes labeling the direction at the
top of the screen (e.g., ahead or behind), labeling the bumper (your bumper), and
possibly other items as well. Also, even though it will reduce the field of view, all
distortion should be removed from the Front/Back interface.
Both the Front/Back Switching and the Aerial view images deserve further development.
The data clearly showed that presenting multiple images on screen simultaneously
(both a front and rear view) increased the time for subject to make decisions,
suggesting the images shown were too small, too complex, or both.
A major surprise was the lack of correlation of any of the measures with each other
except for number of maneuvers and parking time, and the margin of error (mean/sd)
with vehicle contacts. The margin of error finding is important, because contacts are
uncommon, but predicting their frequency without conducting a major experiment is
important.
Finally, although there are no empiric data, it was apparent that many of the subjects
did not know how to parallel park proficiently. They did not know when to begin the first
turn maneuver (when the back ends of the cars are aligned) or when to countersteer.
This information could be conveyed electronically and in the owner’s manual.
57
REFERENCES
Cullinane, B., Smith, D., and Green, P. (2004). Where, When, and How Well People
Park: A Phone Survey and Field Measurements (Technical Report UMTRI 2004-18),
Ann Arbor, Michigan: University of Michigan Transportation Research Institute.
Green, P., Gadgil, S., Walls, S., Amann, J., and Cullinane,B. (2004). Desired Clearance
Around a Vehicle while Parking and for Low Speed Maneuvers (Technical Report 200430). Ann Arbor, Michigan: University of Michigan Transportation Research Institute.
Rubin, R. and Green, P. (2005). Design Principles for Video-Based Parking
Assistance Systems (Technical Report UMTRI 2005-09), Ann Arbor, Michigan:
University of Michigan Transportation Research Institute.
Smith, D., Green, P., and Jacob, R. (2004). Parking and Low-Speed Crashes: Crash
Database, Literature, and Insurance Agent Perspectives (Technical Report UMTRI
2004-9), Ann Arbor, Michigan: University of Michigan Transportation Research
Institute.
Shepherd, R.N. and Metzler, J. (1971). Mental Rotation of 3-Dimensional Objects,
Science, 171, 701-703.
Walls, S., Amann, J., Cullinane, B., Green, P., Gadgil, S., and Rubin, R. (2004).
Alternative Images for Perpendicular Parking: A Usability Test of a Multi-Camera
Assistance System (Technical Report 2004-17). Ann Arbor, Michigan: University of
Michigan Transportation Research Institute.
59
Appendix A – Subject Consent Form
Participant
number: _____
Parking and Low Speed Driving – Inside Subjects
Investigators: Paul Green (763 3795) UMTRI Human Factors
An automotive manufacturer is developing devices to help people park and drive a slow speeds. In this
experiment you will be parking a test car in the UMTRI parking lot a number of times using a vehicle
outfitted with a special camera system to help you park. This system has similarities to those in luxury
cars but is more sophisticated. We will be recording what you do and asking for your preferences for
various system features.
All of the parking will be in the UMTRI lot and at no time should your speed exceed 20 mph. In fact, most
of the driving will be at 3-5 mph, so the risk of a serious crash is minimal.
The results of this study, summarized in a report for the sponsor and the public, will be used to make
future vehicles easier and safer to drive.
There are no risks associated with this experiment other than those associated with ordinary driving. You
may withdraw from this study at any time without penalty. The study should take 1-2 hours. Time spent
as a subject will be covered by the project account. There is not additional compensation.
As noted when you were recruited, to record the process of what drivers do and where drivers look, we
will be recording this experiment on videotape.
----------------------------------------------------------------------------------------------------------------------------I HAVE READ AND UNDERSTAND THE INFORMATION PRESENTED ABOVE. MY PARTICIPATION
IN THIS STUDY IS ENTIRELY VOLUNTARY.
_________________________
Print your name
_________________________
Date
_________________________
Sign your name
_________________________
Witness (experimenter)
----------------------------------------------------------------------------------------------------------------I agree to be videotaped in this study and realize my face will appear on the tape. I understand that
segments from the tapes may be used in presentations to explain the results. My name will not be
disclosed with the tape. The raw tapes will be erased 10 years after the project is completed.
[Optional]:
Sign your name _________________________
Segments from videotapes of my sessions may be used by the media (e.g., on TV) to help explain this
research to the public.
[Optional]:
Sign your name _________________________
Should you have questions regarding your participation in research, please contact Kate Keever:
Human Subjects Projection Office, IRB Behavioral Sciences, 540 East Liberty Street, Suite 202, Ann
Arbor, MI 48104-2210, Ph: 936-0933, fax: 647 9084, email: IRBhsbs@umich.edu, web:
http://www.irb.research.umich.edu
61
Appendix B – Subject Biographical Form
University of Michigan Transportation Research Institute
Human Factors Division
Subject:
Around View Monitor Study Biographical FormDate:
Name:
Male
Female (please circle)
Date of Birth:
Seated Eye Height Ver. (cm)
Weight (kg)
Seated Eye Height Hor. (in.)
Occupation
/
/
mm / dd / yy
Height (cm)
(e.g. mechanical engineer, courier, etc)
What kind of motor vehicle do you drive the most?
year:
make:
model:
Miles you drive per year:
During the past 5 years, in how many:
Parking crashes have you been involved?
Non-parking crashes have you been involved?
How many times per month do you park in:
On Weekdays:
Angular spaces:
On Weekends:
Parallel spaces:
Perpendicular spaces:
In how many previous UMTRI studies have you participated?
Have you ever driven a car with an in-vehicle parking camera?
If you were driving on a 3-lane highway, what lane would you typically drive in?
Left
Center
Right
For Experimenter:
Vision Correction: Yes ( Eye Glass, Hard Contact Lens, Soft Contact Lens), No
Titmus Vision: (Landolt Rings)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
T
R
R
L
T
B
L
R
L
B
R
B
T
R
20/200 20/100 20/70 20/50 20/40 20/35 20/30 20/25 20/22 20/20 20/18 20/17 20/15 20/13
1
2
3
4
5
6
7
8
9
10
11
12
13
14
T
R
R
L
T
B
L
R
L
B
R
B
T
R
20/200 20/100 20/70 20/50 20/40 20/35 20/30 20/25 20/22 20/20 20/18 20/17 20/15 20/13
63
Appendix C – Pretest Script
Hello <Subject’s Name>, my name is <Your Name>, and I am going to get you set up
for this study. The first thing we need to do is to get some paperwork out of the way. So
please fill out this form
Give subject participation form to fill out
This form basically states that you are aware of the type of study being conducted, you
know how long the study will take, and that the study takes place in a car that you will
be driving at low speeds.
In addition, the form also informs you that you will be video taped during the study, and
your video may be used in presentations to explain the results of the test. It also states
that the media may use your video. In both cases, you name will NOT be disclosed
anywhere on or with the video.
Do you have any questions? Then please print and sign your name where appropriate,
and when you are finished, please hand the form to me.
Because this study involves driving, while using an in-car display, we need to know how
good your eyesight is, so we will now do a brief vision test. May I please see your
driver’s license?
Verify validity of license, and make sure birth date is correct.
Ok, please have a seat at the eye test machine.
Clean head pad with alcohol swab.
Ok, for the entire test, please keep looking straight ahead. Can you see that in the first
diamond one of the circles is complete, but the other three are incomplete? For each
diamond, please tell me its number, and the location of the complete circle, top, bottom,
left, or right.
Perform visual acuity test Far #2 without lenses in place.
Ok, good. Now we are going to do a similar test. Again, please tell me the number of
the diamond, and the location of the complete circle.
Perform visual acuity test Far #2 with 80 cm lenses
Because your position within the car will be important we need to get some biographical
dimension data from you. The first measurement that we need to take is your weight.
Please remove your shoes, and empty your pockets of their contents. Please also
65
remove any watches, cell glasses or any other objects you may be carrying. This is also
a good time to turn off any cell phones or pagers that you have.
Measure and record weight.
Next we need to measure your height, so step off the scale and stand up straight next to
our measuring device with your head level to the ground.
Measure and Record height.
Ok, we are ready to go out to the test vehicle. Go ahead and put your shoes back on,
and gather your belongings. This will also be the last time to use the restroom or to get
a drink until the conclusion of the study. If you need to use the restroom or get a drink,
please do so now.
Walk to test car.
This is <Experimenter Name>, and <Experimenter Name>, they will be
helping with the study from here. Please have a seat in the car, and adjust
the seat so you are comfortable. There are controls on the bottom left side
of the seat to control the seat position.
Show subject controls.
When you feel that you are in a comfortable driving position, please place your hands
on your lap, so we may measure your seated eye height. This measurement is
important so we can tell what your field of view was like while in the vehicle.
Measure seated eye height, height first (vertical distance), and then distance from car
reference (horizontal distance).
Very good. We are now going to begin the study. The car is already started, so please
close the door, and adjust your mirrors to your needs.
Show subject control for side mirrors.
66
Appendix D – Parallel Parking Instructions
Parallel Parking Procedure Instructions for CAMERA Project
John Amann, Sean Walls, Sujata Gadgil, Paul Green
Version 1e:jra, July 26, 2004
Part 1: Introduction and Explanation
For this experiment, please sit in the driver’s seat and fasten your seatbelt. Also, please
adjust the seat and mirrors to match your driving needs. The purpose of this
experiment is to determine how using a new camera system affects parallel parking.
We will examine four different camera views in addition to parking without the camera
image. We will park without the camera six times and with the camera 12 times for a
total of 18 parking trials. Each trial consists of entering a parallel spot on the right,
putting the gearshift in park when you are in the final position, and then backing out and
looping around via the near aisle in the parking lot so you can re-enter the same
spot. You will be able to adjust your parking maneuver as often as necessary until you
feel satisfied.
To avoid problems with the cameras, do not turn the car off at any point during the
experiment, even when the experiment is over. Also be very careful when driving and
parking this very expensive car to avoid hitting other cars. Do you have any questions?
Part 2: Vehicle Familiarization
To familiarize yourself with this car, we are going to first simply drive around the parking
lot a couple of times. We want you to get a “feel” for the car. Since you have not likely
driven this type of car before, use this time to get a feel for the size of the car. We
would also like you to park in an empty spot that does not have cars on either side.
Once you have parked the car, please put the car into park, get out of the vehicle, and
examine your parking for distance and alignment within the spot. Use these practice
trials to adjust your feeling of the car’s size to its actual size. We will practice parking in
an empty spot 3 times. Between each parking maneuver, please drive around the lot,
and return to the spot, and re-park. Any Questions?
For the safety of you and our experimenters, I will be making sure that the car
does not pose a hazard to anyone or anything surrounding it. If I feel that the
safety of you or one of the experimenters is in jeopardy, I will ask you to stop the
car so that we can fix the situation.
Ok, please pull around the UMTRI building and drive towards the parking lot on the
other side. Before leaving this lot, make sure to signal and check for oncoming traffic.
We are going to drive clockwise around the parking lot so that you can enter the parking
spot from the right.
67
Good, you will now practice pulling next to the curb. To do this, you will drive around to
the access road and pull as close to the curb as you feel comfortable. Once you are
comfortable, please put the car into park, get out of the vehicle, and examine the
distance between the car and the curb. We will practice pulling next to the curb 3 times.
Between each maneuver, please drive around the lot, return to the spot, and re-park.
Any questions?
After the acclimation trials and when the subject is ready to begin, have him or her drive
around to the testing tent to begin the experiment. The experimenter on foot will hold
up the image and trial number to the car, and then in front of each camera. The
experimenter inside the car will verify the image order on the Image Selection Sheet
and will adjust the CAMERA system so that the appropriate image is displayed on the
monitor.
Part 3: Parking Protocol (Trials 1-3: Control Trials)
Please drive a counter-clockwise loop around the parking lot. This first set of parking
maneuvers will be done without the camera system.
The in-vehicle experimenter should ensure that the CAMERA system display is turned
off. While subject is driving, the experimenters should ensure that at no time is the car
in a position to cause or receive damage.
As the car approaches the parking spot (which should be on the right), say:
Next, pull up to the front vehicle (blue Infiniti) and put the vehicle into park when you
believe your vehicle is in position to begin a parallel parking maneuver. After putting the
vehicle into park and letting the vehicle settle, you may then put the gearshift into
reverse and begin a parallel parking maneuver. When you are satisfied with your
parking result, put the shifter into park, stop the car and let me know.
After the subject is satisfied with his or her parking result, motion to the on-foot
experimenter, who will hold a clipboard in front of the car and cameras showing the next
image number to be tested. The experimenter inside the car will verify the image order
on the Image Selection Sheet.
When you are ready, please pull the car out of the spot and loop around the parking lot
to begin your next trial. We will be performing the same maneuver. Simply pull up to the
front vehicle and put the car into park where you would begin your parallel parking
maneuver. Then put the shift into reverse and being your parallel parking maneuver.
When you complete your trial, please straighten the wheels and put the car in park to
signify that you have finished parking.
Repeat Part 3 until all 3 trials are complete.
68
After the subject is satisfied with his or her parking result, motion to the on-foot
experimenter, who will hold a clipboard in front of the car and cameras showing the next
image number to be tested. The experimenter inside the car will verify the image order
on the Image Selection Sheet. Tell the subject to remain in park for a few minutes.
Turn on CAMERA system display and adjust the CAMERA to the appropriate image.
Part 4: Parking Protocol (Trials 4-15 with CAMERA)
While the vehicle is still in park, presentation of the images should be done. Make sure
the display is on the right image.
Here is the first image that is intended for assisting you during a parallel parking
maneuver. Do you have any questions about what this image shows? Feel free to ask
any questions at this time or at any time in which the vehicle is in park. As it is
important for you to pay attention to the road and your parking maneuver, please do not
ask any questions while the vehicle is in motion. When you feel comfortable with this
image, we can continue. Please exit the parking space and loop around the parking lot.
Park in the manner that you have been previously instructed while trying to use the
system as much as possible.
After the subject is satisfied with his or her parking result, motion to the on-foot
experimenter, who will hold a clipboard in front of the car and cameras showing the next
image number to be tested. The experimenter inside the car will verify they image order
on the Image Selection Sheet
Repeat Part 4 until all 12 trials are complete. At each new image presentation, ask “Do
you have any questions for this image?”
Part 5: Final Control Trials and Post-Test Evaluation (Trials 16-18 without Camera)
Repeat Part 3 for last 3 control trials.
After the final trial is completed, the on-foot experimenter should verify there are no
missing data points on the data collection sheet, and everything written is legible. If
something is uncertain, cross out the value and write the correction next to it – do not
erase or write over data. If everything is accounted for, signal to the interior
experimenter.
When the on-foot experimenter gives the go-ahead signal, the in-vehicle experimenter
should say:
We now would like you to complete a brief post-experiment evaluation regarding the
camera system’s usability. Please shift into park and leave the car running.
69
After the subject completes the evaluation, the in-vehicle experimenter should verify that
everything is legible. If something is uncertain, cross out the value and write the
correction next to it – do not erase or write over data. If everything is accounted for, say:
We have completed this experiment. Here is your payment and we thank you for your
time.
70
Appendix E – Post-Evaluation Form
SUBJECT POST-EXPERIMENT EVALUATION
IMAGE 1: Rate image 1 by placing a tick mark on the scale below
1
2
3
4
5
6
7
8
9
Extremely Useless
10
Extremely Useful
IMAGE 2: Rate image 2 by placing a tick mark on the scale below
1
2
3
4
5
6
7
8
9
Extremely Useless
10
Extremely Useful
IMAGE 3: Rate image 3 by placing a tick mark on the scale below
1
2
3
4
5
6
7
8
9
Extremely Useless
10
Extremely Useful
IMAGE 4: Rate image 4 by placing a tick mark on the scale below
1
2
3
4
5
6
7
8
9
Extremely Useless
10
Extremely Useful
IMAGE 5: Rate image 5 by placing a tick mark on the scale below
1
2
3
4
5
6
7
8
9
Extremely Useless
10
Extremely Useful
IMAGE 6: Rate image 6 by placing a tick mark on the scale below
1
2
3
4
5
6
Extremely Useless
7
8
9
10
Extremely Useful
How has the AVM system changed your parking ability?
71
1
2
3
4
Made Much Worse
5
6
7
8
9
No Change
10
Made Much Better
How comfortable does the AVM make you feel about parking?
1
2
3
4
5
6
7
8
9
Very Uncomfortable
10
Very Comfortable
Do you feel safer in your vehicle while using the AVM system?
Yes
No
Did you find yourself using the AVM system as a
supplement to your mirrors or as an alternative?
Supplement
Alternative
Do you feel it took more or less time for you to park?
More time
Less Time
Which image did you find most helpful and why?
Did you feel the AVM system created hazards to your parking ability? Is so, what hazards?
Which image or parts of an image were confusing and why?
How would you solve these problems?
How much do you like the AVM system overall?
1
Strongly Dislike
2
3
4
5
6
7
8
How much would you be willing to pay for the AVM system in your vehicle?
$_________________
72
9
10
Strongly Like
Appendix F – Testing Equipment List
Name
Device
Location
1
Front Corner Camera
VCR
Panasonic AG-D5550 Video Cassette
Recorder
Test Tent
2
Front Center Camera
VCR
Panasonic AG-D5550 Video Cassette
Recorder
Test Tent
Curb Camera VCR
Rear Center Camera
VCR
Quad Splitter
Panasonic AG-D5550 Video Cassette
Recorder
Panasonic AG-1970 Video Cassette
Recorder
Panasonic WJ-450 Color Quad System
3
4
4
5
6
13-inch Sony Trinitron PVM14N1U Color
Monitor
Test Tent
Test Tent
Test Tent
7
TV Monitor
Power Generator
All Closest Approach
Cameras (x4)
9
Overview Camera
SuperCircuits PC197
Test Tent
Test Tent
Above Parking
Spot
Above Test
Space
10
13
Wireless Transmitter
Wireless Receiver
Supercircuit ML10WR 2.4 GHz
transmitter
Supercircuit ML10WR 2.4 GHz receiver
Above Parking
Spot
Q45
14
Face Camera
EIA Model KPC-S400 black and white
camera
Q45
15
Dash Camera
16
12VDC Power Supply
KT&C Color B136956 camera
Radio Shack 120 VAC à 12 VDC
Converter Cat. No. 22-127E
17
Quad Splitter
Super Circuits QS7 Video Color Quad
Processor
Q45
18
Video Mixer
Videonics Digital Video Mixer Model: MX1
Q45
SuperCircuits PC165c CML2-10MMZ
Q45
Q45
19
Video Converter
20
Small LCD Screen
Viewsonic UB50HRTV Video Converter
Model: USACC23126-1M
Mitsubishi TTF Active Matrix 5.5 inch
(Diag.) Car Color Display Model: DU9450M
21
Large LCD Screen
Viewsonic VE510+ 15 inch (Diag.)
Monitor Model: VLCDS23587-2W
Q45
22
In-Car VCR
Panasonic UG-5700 VHS Recorder
Q45
23
Audio Mixer
Shure Sound Mixer Model: M267 Series
Q45
73
Q45
Q45
Appendix G – UMTRI East Lot Layout
75
APPENDIX H - DRIVER COMMENTS
Comment Category
1= Comments About Specific Images
2= Comments About Cameras/Conceptual
3= Driving or Car Related Comments
() Indicates interpreted quote
Image/Interface
0 = Control
1 = Front/Back Switching
2 = Front Back Combined
3 = Aerial
4 = Aerial Combined
Image
1
1
6
8
9
13
13
2
2
2
2
2
1
3
0
0
0
0
0
0
0
3
9
2,3
1
1
1
11
13
1
1
1
1
13
1
1
Subject
Category
Table 22. Subject Comments During Experiment (Sorted by Interface)
Comments
I definitely have a lot more nerve when I have the
cameras.
The cameras definitely make it a lot less stressful.
I can't really see the back and sides.
Now, I miss the camera being there, I'm looking for it.
You don't show that, we might have troubles now.
You get closer to the curb for sure with the aerial view.
I'm using my rearview mirror a lot.
The camera I definitely feel is a help. Especially cause,
you know, I'm driving a car I'm not used to.
Ok, now where are we on this? Is that us?
Wish there was an image to show me how close I a to the
curb. Ideally if they could tell me how many inches I am
away from the curb. The optics here are misleading.
What is this here? [Asks what the rear image is showing]
Know why I don't like it? You can't see the line, the curb
on this. I mean I'm doing this by sense, but I'm not getting
a sense of the curb. And I don't have a sense, and I'm
almost on top of the car. I can and, at least I feel I am.
And I can't tell how far I am from the curb, and I can only
tell how far based on the car in front of me, but I'm not I'm
farther from the curb. I don't like this at all.
13
1
1
13
1
1
13
1
1
13
14
1
1
1
1
15
1
1
15
1,3
1
9
9
9
1
1
2
2
2
2
10
1
2
10
1
2
11
1
2
15
15
16
1
1
1
1
1
2
2
2
3
1
1
1
1
3
3
Now, I can't tell how close I am to the car behind me, the
other one you know I could tell, you could just tel, when
you were going to, I just can't, this perception here is not
fine enough. It doesn't give you enough sense of where
you are. You have to depend more on your innate sense of
parking ability.
Look how, this, how, look how this shows I'm so far away.
I mean it looks like, ya know, thirty feet away. Then you
can't tell how far you're going into the curb, so I'm really
depending on my senses. Pretty close, I would never
know I was this close.
Now, how can I tell? I feel like I'm right on top of that car.
But look at how far, look how far it looks away, but I feel
like I'm right on top of it. Yes, very much so, it looks like
you're far away and you're not well you are a little bit.
This is the front of the car behind me? Then it shouldn't
say back… Yes, it would help if the label was down at the
bottom.
This is hard to tell if the camera is aimed.
Well, like I said, I have no perception of what this really is.
And the curbs could really help me here.
Now, without the camera I would stop, with the camera I'll
keep going [Image 1 back]
I saw that if I was backing up I finally saw myself the rear
of that vehicle but as far as working alignment, it just
doesn't register in my mind.
Like I said I don't find this thing I'm looking at.
I'm not comfortable at all with this [camera system].
Now, this one's alright too. Except in foot measurements.
Ya know, what good is it, unless the first time you use it
you get out and find if this image is three fee [back] and
this image is two feet [front].
I was thinking that if they have 5, 4, 3, 2, 1 for people with
bad vision that could flash, like a digital readout, LED, …,
yeah, that would really be good.
Cause I'm trying to calibrate my eyes to the image or the
reality of the situation.
I understand this better if this car was behind this [Front
behind Back]
This image is so totally foreign to me it is not helping me.
I definitely like this one.
You know I'm really not using these cameras at all.
Yeah, the aerial view is going to be the toughest just
because it is so distorted.
Yeah, I don't really know if I can trust this thing for corners.
78
3
6
1
1
3
3
10
10
1
2
3
3
13
1
3
13
1
3
13
13
1
1
3
3
13
13
15
1
2
1
3
3
3
15
3
3
1
1
4
5
6
1
1
4
4
6
1
4
8
1
4
11
1
4
Cause one thing I noticed about that one [image 3] Like
the back and front labels ended up taking up a large
percentage of the screen.
(Confusion about orientation of bottom image of #3)
Is there any dimensions here, is this a foot? So how do
you know when you're a foot away? … I wonder why they
don't have foot marks.
You know I really find this no help at all.
Well, here I am, is this me? I can't…This is back?…No,
I'm not sure it'll apply to what I'm doing but.
I love this one, this one because you just get such a, a
much better picture. … Right, I'm not so sure these are as
helpful as this [left side of image as opposed to right side
of image]. I mean you don't have a, well I guess you can
see your curb, but this is so great.
And I love it how you can tell how far you are from the car.
Oh, I love it.
I have no use for this [the left side]
Whether someone developed just this side, their focus was
aerial, I don't even get this [the left side]. I don't even use
it at all. … [In response to the image being stretched in the
aerial view] No, it doesn't bother me. Knowing this little
distance between your rear and the front of the other car
and seeing just about when you're going to close or touch
it is very informative..
This is very hard to use this thing.
I don't even use that [left side]
The curb is helping me more then anything…bumping the
curb.
I'm finding this kind of useful when I'm judging close to the
curb, but it's still a little tricky judging the distance to the
back.
I think this is the best image. The other images are too
confusing.
(Back image distortion on aerial)
I don't really know if it would help me as much as I thought
it would….I don't know, like the other images are really
blurry, like I can see the car in front of me but I can't, is this
the car behind me? This part [the back part of the image]
is confusing.
This view is nice for pulling out of spaces, it helps you see
the sides of your car.
I can't tell where I am and what's the curb. I'm further
away from the curb but the image shows me I'm right on
top of the curb. Also, the top image setup doesn't look like
79
13
1
4
13
3
4
14
1
4
15
1
4
15
15
1
2
4
4
12
3
0,1,2
1
2
1,2,3,0
1
1
6
11
2
3
3
3
1,2,3,0
1,2,3,0
1,2,3,0
1,2,3,4
it's a real car, it looks animated.
I really do use this, this is great.
I'm not even using my rearview mirrors. This is a crutch,
BAD!
(It's hard to tell between the bumper of the car and the
shadow.)
I think before I start using this, I should be able to use this,
I don't know how much space I really have. If beforehand I
could see how much space I really have to hitting this,
that would help.
I think it would be a good idea to get out and see what it
[Image 4] really meant.
I'm very uneasy using this.
I've gotten it down a lot better, but now I'm hitting the curb
a lot more.
I really hate this extra camera system. It's not even the
images being distorted. But I'm used to looking at where
the rear car is in relation to the window pillars, and I guess
I use those a cues already. The curbs are such a small
part of the camera's field of vision.
Now, instead of the side ones I could really use like the
corner ones.
This is definitely a huge car.
(Subject has good sense of front right corner)
(Because of time of day, shadows are an issue.)
80