Collision Warning Design1 Collision Warning Design To Mitigate Driver Distraction (CHI 2004) Andrew Muller & Eugene Khokhlov

Collision Warning Design2 University of Iowa John D. Lee Ph.D. Elizabeth Hayes Daimler Chrysler (Chewbacca) Joshua D. Hoffman Grad Student

Collision Warning Design3 To The Point: The Problem: Too many distractions while driving a car The Need: Collision warning system

Collision Warning Design4 Background Information In-vehicle Information Systems (IVIS) are now feasible because: Technology Advances Societal Trends IVIS Functionality Response Types Critical Factors for IVIS

Collision Warning Design5 Alert Strategies Warning Strategies Graded Single Staged Sensor Modality Presentation Haptic (touch) Auditory

Collision Warning Design6 Experiment Goals Experiment 1 Examine how driver response depends on graded and single stage warnings Examine how driver response depends on modality (haptic vs. auditory) of the warning Experiment 2 Examine how these warning strategies and modalities affect driver preference

Collision Warning Design7 Experiment 1 Method A mixed between/within-subject experimental design 3, 15-minute driving scenarios 21 braking events (7x3)=21 3 levels of severity Speech-based system to distract the driver

Collision Warning Design8 Participants 40 individuals 20 female, 20 male Ages of 25 and 55 (licensed) Unaware of the nature of the research Paid $20 each

Collision Warning Design9 Apparatus Fixed-based, medium-fidelity driving simulator 1992 Mercury Sable 50-degree visual field of view 640x480 screen Visual collision warning icon Needed elements for auditory and haptic alerts

Collision Warning Design10 DriveSafety (Hyperion)

Collision Warning Design11 Experimental Design and Independent Variables Mixed between-within subject design Between subject variables Warning modality Warning strategy Within subject variables Severity of lead vehicle breaking If response was require

Collision Warning Design12 Dependent Variables Safety benefit Number of collisions Adjusted minimum time to collision (AMTTC) Driver response process (response followed by assessment or assessment followed by response)

Collision Warning Design13 Procedure Operation instruction Introductory drive (5 min) 3 main drives (15 min/each) 7 braking events per 55mph 1/7 was severe, always at end Complete auditory task

Collision Warning Design14 Results 741 data points total Repeated-measures ANOVA was used to analyze the data using two-tailed hypothesis tests

Collision Warning Design15 Results – Severity of braking events and driver response Drivers responded to braking events in a systematic and realistic manner AMTTC reflected braking severity Severity of lead vehicle braking affected drivers’ braking response Severity of braking affected mean deceleration

Collision Warning Design16 Results – Interface characteristics and safety benefit (collisions) 40 potential collisions 10 collisions occurred 7 in single-stage and 3 in graded X 2 (1)= 2.13, p= in auditory and 5 in haptic

Collision Warning Design17 Results – Interface characteristics and safety benefit (AMTTC) Slight benefit for graded compared to single-stage F(1,36)=8.74, p= Graded substantially better in severe braking events

Collision Warning Design18 AMTTC

Collision Warning Design19 Response to nuisance alarm braking events

Collision Warning Design20 Experiment 2 Method A within-subject experimental design 4, 10-minute scenarios 24 braking events 3 levels of severity 2/3 of events required no driver response

Collision Warning Design21 Participants 20 individuals 11 females, 9 males (licensed) Between the ages of 25 and 55 Unaware of the nature of the research Paid $20 each

Collision Warning Design22 Apparatus & Independent variables and experimental design Same as in experiment 1

Collision Warning Design23 Dependent variables Driver attitudes were measured with a series of subjective rating scales after each drive After completion of all trials, they comparatively ranked the systems

Collision Warning Design24 Procedure Operation instruction Introductory drive (5 min) 4 main drives (10 min/each) 6 braking events per drive Each scenario had an equal number of event severity

Collision Warning Design25 Results Rank the warning modalities in order from 1 to 4 based on preference Violation of assumption of a repeated measures ANOVA Applied Friedman’s non-parametric analysis Only when Friedman’s showed a significant difference between conditions was a post-hoc multiple comparison performed using Fisher’s least significant difference method

Collision Warning Design26

Collision Warning Design27 Conclusions Graded warning provided a greater safety margin Graded warning induced fewer inappropriate responses to the nuisance alarms Graded warning was more trusted Warning modality had little effect on performance in severe braking events Haptic warnings were preferred on several dimensions to auditory

Collision Warning Design28 Questions In table 2, graded haptic beats single-stage haptic in everything except overall preference, what can account for this? Does the data on table 2 match what you would have expected? Graded is preferred for a one hour experiment, how about 5-10 years on daily basis?

Collision Warning Design29 Questions Haptic is preferred over auditory in this study, is this a property of auditory or a property of the time span of the test, or some other factor? Why express haptic through a seat and not a gas pedal as in previous studies?