Cell Phone Ring Suppression and HUD Caller ID:
Effectiveness in Reducing Momentary Driver
Distraction Under Varying Workload Levels
UMTRI Technical Report 2001-29
Christopher Nowakowski, Dana Friedman & Paul Green
1
University of Michigan
Ann Arbor, Michigan, USA
Issues
1. Does the location of a caller ID display and phone buttons affect either the time to
answer the phone or driving performance?
2. Does the presence or absence of an auditory ring (where the HUD caller ID
indicated a call) affect either the time to answer the phone or driving performance?
3. Does increased driving workload affect either the time to answer the phone or
driving performance?
4. What were the initial driver reactions to a HUD-based call timer?
2
Test Plan
Ring Timing (s)
Driving Workload Levels
and Possible Ring Locations
Straight
Moderate
(r=582 m)
10
Sharp
(r=194 m)
Caller ID and Button Locations
Caller ID
Test Participants
5
N=24
0
-1
Older
(60-75)
Younger
(18-30)
3
Increasing Workload
Buttons
Female
Male
6
6
6
6
Results and Conclusions
8
7
6
5
4
3
2
1
0
Ring
No Ring
Ring
No Ring
60
50
40
Older
30
20
10
Younger
Center HUD
Console Center
HUD
Center
HUD Baseline Center HUD HUD
HUD
Right Driving Console Center Center Right
Caller ID Location
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0
Line-Crossing Rate (%)
Response Time (s)
Issue 1: Effects of caller ID and button location
Issue 2: Effect of auditory ring
16
14
12
10
8
6
4
2
0
Ring
Silence
Ring
Percentile
HUD Center
w/o Ring
HUD Center
w/Ring
No. of
Drivers
Ring/No Ring Difference
10/24
Response time unaffected
9/24
Response time slowed
5/24
No consistent RT trends
24/24
0
1
2
3
4
5
6
Response Time (s)
7
Driving performance
unaffected by the ring
8
Issue 3: Effect of driving workload
10
8
6
4
2
0
Response Time (s)
Curvature
9
3
0
Center
Console
HUD
Std Dev Lane Position (ft)
Line-Crossing Rate (%)
70
2.0
60
1.5
50
40
1.0
30
20
0.5
10
0.0
0
Baseline Center HUD
Baseline Center HUD
Driving Console
Driving Console
Caller ID Location
Issue 4: Driver reactions to call timer
a. Seventy percent of drivers did not want to see the call timer.
b. All drivers wanting the call timer also preferred the center HUD location.
c. Many commented that they didn’t notice the call timer in any of the locations.
4
Design Recommendations
Design Parameter
Recommendation
Caller ID Location Use a central HUD location (e.g., within approximately
5 degrees down and 5 degrees right or left from center).
Button Locations
Use steering wheel buttons for “Talk” and “End.”
Auditory Ring
Response time data suggests that the use of short auditory alerts
(1 second or less) might be less distracting, but more research
on other rings (including musical rings) is needed.
Call Timer
Preference data indicated that drivers did not want to see a call
timer that was continuously updated on the HUD.
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