Date of Award

Spring 2011

Document Type


Degree Name

Doctor of Philosophy (PhD)



Committee Director

James P. Bliss

Committee Member

Bryan E. Porter

Committee Member

Patricia Ellison-Potter


This field experiment tested the effects of two systems on speeding, mental workload, and driver acceptance of the systems. Using GPS technology integrated with GIS referenced speed limit information, eight vehicles were instrumented in a manner that allowed real time knowledge of vehicle speed relative to the speed limit. Fifty participants drove these vehicles, with each individual driving his or her assigned vehicle for a four week trial. During one week, 40 participants experienced an automated feedback system, which provided visual and auditory alerts when they sped five or more mph over the limit. Twenty of these 40 individuals experienced a monetary incentive system during their second and third weeks of driving. Ten participants were in a control group that experienced neither system. Results indicated that the incentive system resulted in dramatic reductions in speeding over the posted limit, and the feedback system led to modest reductions in speeding. In the condition in which drivers experienced the feedback and incentive, reductions in speeding were similar to those found during the incentive only condition. Drivers perceived that both systems increased mental workload. Ratings of trust and acceptance were generally positive, although drivers reported the feedback system was annoying and displeasing. The results indicate that these systems could significantly benefit traffic safety by reducing crashes caused by speeding.