Comparing Handheld and Voice-Control
Interfaces When Using Mobile Phones and Portable Music
PlayersFriday, December 17th, 2010
Justin M. OwensShane B. McLaughlinJeremy Sudweeks
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Introduction
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Background: Increasing number of electronic devices used in vehicles, requiring drivers take eyes off road.
Purpose: Determine whether a voice-control system offers driving performance advantages over manual control of mobile phones and music players.
Conducted on public, rural 65 mph roadway.
Tested 21 regular users of the voice-control system to avoid practice effects; younger (~20’s) and older (~40’s) age groups.
SYNC Voice-Control System
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IntroductionMethodologyProceduresAnalysisResultsConclusions
System allows voice commands for dialing (“Call John Doe”) & MP3 track selection (“Play track Enter Sandman”), handsfree conversation
Also implements text-to-speech text message reception and canned message sending*
Experimental Design
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IntroductionMethodologyProceduresAnalysisResultsConclusions
AgeYounger
Older
ModalityHandheld
SYNC
Task(Baseline)
Dial ContactConversation
Play Track
BetweenSubjects
WithinSubjects
Dependent Variables Task Duration
First -> Last task-related movement
Task-Related Interior Glances Number of Glances Glance Duration
Steering Measures Steering Variance Max Steering Wheel Speed
Mental Demand 1-7; Subscale of NASA TLX
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Test Vehicle 2010 Mercury Mariner with
SYNC®
VTTI Instrumentation Four cameras Cabin audio Accelerometers Gyros Forward radar CAN connectivity for
Steering wheel angle Speed Brake on/off
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Handheld Devices Participants used personal mobile phone and
portable music players for the handheld trials.
Phones: 10 - Numeric physical keyboards 7 - Touch screens 4 - QWERTY keypads
Music Players: 12 - Apple iPods with click-wheel 4 - Touch screen (2 iPhones and 1 iPod Touch) 5 - Other interfaces, including 1 Zune
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Testing Procedures 1.9 miles, 65 mph Completed 6 laps One task per leg,
after participant reached comfortable speed
Two trials each Handheld Dial Handheld Play Handheld Converse Voice Dial Voice Play Voice Converse
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Task
Task
Analysis
Video analyzed by trained reductionists
Separate General Linear Models were conducted for all measures.
Post-hoc comparisons conducted using Tukey correction.
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IntroductionMethodologyProceduresAnalysisResultsConclusions
VehicleMATLABMS SQL MS SQL
Video Reduction
Phone/MP3: Total Interior Glance Duration
Handheld Dial, Play had longer total eyes-interior duration than any other condition, including Baseline.
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IntroductionMethodologyProceduresAnalysisResultsConclusions
0
5
10
15
20
25
30
Younger
Older
Dial Contact Play Track ConversationBase-line
A AA AA
B
C
0
0.5
1
1.5
2
2.5
3
Baseline Handheld Voice Handheld Voice Handheld Voice
Stee
ring
Varia
nce
(deg
)Younger
Older
Dial Contact Play Track ConverseBase-line
AA
A A
BB
A
Phone/MP3: Steering Variance
Handheld Dial, Handheld Play higher steering variance than all conditions except each other.
Differences not found between Voice and Baseline. Older drivers had more variance.
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Results
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IntroductionMethodologyProceduresAnalysisResultsConclusions
Handheld dialing and music selection resulted in: Longer time to complete tasks More interior glances Longer total glance duration More steering variability Faster (jerkier) steering corrections
All tasks had higher reported mental demand than baseline, but handheld tasks were rated the highest.
Voice control and conversation rarely differed from baseline measures.
Conclusions Voice-control for placing calls and selecting tracks
had less impact on driving than manual control.
No performance differences were found between voice and manual tasks during conversations.
In general, measures during conversation were not found to be different from baseline driving.
Older drivers had more difficulty during manual dialing and track selection.
All tasks had higher reported mental demand than baseline, but handheld dialing/music were highest
IntroductionMethodologyProceduresAnalysisResultsConclusions
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Acknowledgments & References Thanks to Ford Motor Company for funding
and test vehicle. John Shutko, point of contact
Owens, J.M., McLaughlin, S.B., & Sudweeks, J. (2010). On-Road comparison of driving performance measures when using handheld and voice-control interfaces for mobile phones and portable music players. SAE Int. J. Passeng. Cars – Mech. Syst. 3(1): 734-743.
*Owens, J.M., McLaughlin, S.B., & Sudweeks, J. (In Press), Driver performance while text messaging using handheld and in-vehicle systems. Accid. Anal. Prev., doi:10.1016/j.aap.2010.11.019
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Questions?
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Summary: Comparison to Baseline
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Task Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Hand
held
SYN
C
Dial na na - - - - - - - -- -Play na na -- -- -- -- - - - -- -- -
Converse na na - -- -Receive Text na na - - - -
Send Text na na -- - -- - -- - -- - - -- - -- -
No difference found between - Difference found-- Larger difference found
Max SW Velocity
Number of SW
reversals
Subjective Mental
DemandTask
Duration
Total Duration
of Interior Glances
Number of Interior
Glances
Maximum Duration Interior Glance
Mean Interior Glance
DurationSteering Variance
p < 0.05
Summary: Voice compared to Handheld
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p < 0.05
TaskTask
Duration
Total Duration of
Interior Glances
Number of Interior Glances
Maximum Duration Interior Glance
Mean Interior Glance
DurationSteering Variance
Max Steering Wheel
Velocity
Number of Steering Wheel
Reversals
Subjective Mental
DemandDial S S S S S S S S SPlay S S S S S S S S S
Converse NA SReceive Text S S S S S S S
Send Text S S S S S S S
SYNC Better Manual Better No difference found