Illusion of Motion, Variation in Value of Travel Time Under Different Freeway Driving Conditions

This paper explores drivers’ subjective value of time under moving and stopped freeway travel conditions with a stated preference survey. Unlike previous studies that assumed a constant value of time, this research relates perceived satisfaction of a freeway trip to its quality indicators. Sixty-nine subjects in Minneapolis - St. Paul, Minnesota, were asked to rank 16 driving scenarios in four condition sets with different durations of ramp wait and freeway travel. Several utility functions were specified in which the weight of ramp delay was a function of the length of the delay and subject-specific variables; the resulting choice models were estimated with rank-ordered logit, binary logit, and rank-ordered mixed logit techniques. Results suggest that drivers perceive ramp wait as more onerous than freeway travel. They also weight each minute of ramp wait more heavily as the delay increases. Subjects showed some tolerance to the first several minutes of ramp delay (less than 5 min) but perceived long delays as up to 12 times more onerous than time in motion. The derived weighting function for ramp wait can improve the design of freeway traffic control strategies that trade off freeway delay with ramp wait. The findings also enable a more utility-based approach for freeway operations than the current method, which has the engineering efficiency objective of minimizing total system delay or maximizing throughput. Minimizing total perceived travel time is probably more appropriate than minimizing total absolute travel time, which does not take into account driver acceptance. The weighting function can be easily transformed into a value-of-time function for project evaluation purposes