Driver Distraction:
A view from the simulator
Frank Drews & David Strayer
Distracted Driving and Multi-tasking...
Research Questions
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Does conversing on a cell phone interfere with driving?
What are the sources of the interference?
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Who is affected?
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Peripheral interference (dialing, holding the phone)
Attentional interference (cell phone conversation)
Are there age / expertise effects?
How much are drivers affected?
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How significant is the interference?
How do other cell phone activities compare?
How do other types of conversation compare?
Simulator-Based Studies
Does conversing on a cell phone interfere with
driving (Experiment 1)
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Car-following paradigm
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Conditions
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Follow periodically braking pace car
Required timely and appropriate reactions
Hands-free cell phone (positioned in advance)
Naturalistic conversations
Single vs. dual-task
Low vs. moderate density *
Measures
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Reaction time
Following distance
Rear-end collisions
Single
Low
Mod.
Dual
Reaction Time
1150
Reaction Time
1100
1050
1000
Single
Dual
950
900
850
800
Low Density
Moderate Density
Following Distance (Meters)
Following Distance
30
29
28
27
26
25
24
23
22
21
20
Single
Dual
Low Density
Moderate Density
Rear-end Collisions
Rear-end Collisions
3
Single
Dual
2
1
0
Low Density
Moderate Density
Summary (Experiment 1)
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Cell-phone driver’s
 Slower reaction times
 Drivers compensate by increasing following distance
 Increase in rear-end accidents
Cell-phone interference
 Naturalistic conversations
Why Do Cell Phones Cause Interference?
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From earlier studies, no interference from:
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Radio broadcasts (audio input)
Books on tape & recorded conversations (audio/verbal input)
Simple shadowing (audio/verbal input, verbal output)
Implies active engagement in conversation necessary
Impairments from both hand-held and hands-free units
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Implies central / cognitive locus
Inattention-blindness (Neisser, Simons)
Inattention-Blindness (Experiment 2)
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Is there cell-phone induced
inattention blindness?
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Hands-free cell phone
Naturalistic conversation with confederate
Eye tracker
Two phases to the study:
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Phase 1: Single & dual-task driving
Phase 2: Recognition memory tests for objects
encountered while driving
Conditional Recognition Probability
Recognition Memory Given Fixation
0.6
0.5
0.4
0.3
0.2
0.1
0
Single-Task
Dual-Task
Summary (Experiment 2)
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Cell phone conversations create inattention blindness
for traffic related events/scenes
Cell phone drivers look but fail to see up to half of the
information in the driving environment
No evidence that cell phone drivers protect more traffic
relevant information
Are there age / experience effects?
(Experiment 3)
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Car-following paradigm
 Follow periodically braking pace car
 Required timely and appropriate reactions
 Hands-free cell phone (positioned in advance)
 Naturalistic conversations
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Performance Measures
 Reaction time
 Recovery time
 Driving speed
 Following distance
Single
Younger Adults
Older Adults
Dual
Brake Reaction Time
1200
Reaction Time
1100
1000
Single
Dual
900
800
700
600
Younger
Older
Summary (Experiment 3)
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Main effect of single vs. dual-task:
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Main effect of age:
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Reaction time
Following distance
Slower reactions
Slower driving speed
Greater following distance
No Age x Task interaction
How Significant is the Interference?
The drunk driver (Experiment 4)
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Cell-phone vs. drunk-driver
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Redelmeier and Tibshirani (1997) suggested that “the relative risk [of
being in a traffic accident while using a cell-phone] is similar to the
hazard associated with driving with a blood alcohol level at the legal
limit” (p. 465).
Cell-phone Driver vs. Drunk Driver
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Car-following paradigm
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Follow periodically braking pace car
Required timely and appropriate reactions
Conditions
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Single-task driving
Cell-phone driving *
Intoxicated driving (BAC= 0.08 wt/vol)
* Hands-free = Hand-held
Reaction Time
1050
Reaction Time
1000
950
900
850
800
750
700
Intoxicated Driving
Cell-Phone Driving
Following Distance (meters)
Following Distance
29.0
28.5
28.0
27.5
27.0
26.5
26.0
25.5
25.0
Intoxicated Driving
Cell-Phone Driving
Rear-end Collisions
Rear-end Collisions
4
3
2
1
0
Intoxicated Driving
Cell-Phone Driving
Summary (Experiment 4)
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Compared to drunk drivers, cell-phone drivers
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React slower
Increase following distance
Compensate by increasing following distance
But: Still more rear-end accidents
When controlling for time on task and driving conditions, cellphone drivers’ performance is worse than that of the drunk driver
Other cell phone related activities: Text
messaging (Experiment 5)
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Car-following paradigm
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Conditions
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Follow periodically braking pace car
Required timely and appropriate reactions
20 friend dyads
Single vs. dual-task
Measures
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Reaction time
Following distance
Minimum following distance
Rear-end collisions
Single
Dual
Reaction Time
1100
Reaction Time
1050
1000
950
900
850
800
750
700
single task
dual task
Following Distance (meters)
Following Distance
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
mean
min
single task
mean
min
dual task
Rear-end Collisions
Rear-end Collisions
7
6
5
4
3
2
1
0
single task
dual task
Summary (Experiment 5)
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Test messaging drivers
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Slower reaction times
Increased following distance
But: smaller minimum distance
Increase in rear-end accidents
Things can be worse: Text messaging exceeds cell phone
conversations in accident risk
Other types of conversations: Cell Phone vs.
Passenger Conversations (Experiment 6)
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Conditions
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Single task / dual task
Conversing on cell phone
Conversing with passenger
Single
Dual
Passenger
Design
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Task (2) x Condition (2)
Cell
Cell Phone vs. Passenger Conversations
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Free driving paradigm
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8 miles of highway
Exit highway at rest area
Hands-free cell phone
Close call stories / friends
Performance Measures
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Lane keeping
Navigation task
Traffic references
Lane Keeping Errors
1.2
1
RMS Error
0.8
0.6
0.4
0.2
0
Single-Task
Passenger
Cell Phone
Successful Navigation
100
80
% Correct Exit
60
40
20
0
Single-Task
Passenger
Cell Phone
Traffic References
4
Number of References
3
2
1
0
Passenger
Cell Phone
Summary (Experiment 6)
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Cell-phone conversations
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More lane keeping errors
More navigation errors
Fewer references to traffic
Passenger conversations
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Collaborative problem solving
Shared situation awareness
Passenger actively supports the driver
The answers
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Does conversing on a cell phone interfere with driving?
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What are the sources of the interference?
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Peripheral interference (dialing)
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Attentional interference (inattention blindness)
Who is affected?
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Yes
Younger and older drivers equally affected
How significant is the interference?
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Worse than listening to radio/books on tape
Worse than in-vehicle conversations
Worse than driving while legally intoxicated
BUT: Less significant than text messaging