The effect of variability of travel time on route and time-of-day choice

This dissertation examines commuters' route and scheduling choices in face of travel time uncertainty. A theoretical model is developed to analyze commuters' joint decisions of route and departure time in a simple origin-destination network with two parallel routes; one route passes through free congested lanes on a freeway, whereas a portion of the other consists of free-flowing lanes with time-varying toll. By accounting for trip distance, the theoretical model is able to examine two different sources of travel time uncertainties: that from the length of commute and type of route.; The dissertation has also fit various discrete choice models to measure value of time and reliability. The data come from a mail survey conducted in 1998 about commuters on State Route 91 in Orange County, California; these commuters choose between a free and a variably tolled route similar to the theoretical setup. The distribution of travel times across different weeks is measured using loop detector data for each route at each time of day and for each day of the week. The best-fitting models represent travel time by its median, and unreliability by the difference between the 90th percentile and the median; the values of time and reliability are measured by examining commuters' route choice both alone and combined with other choices, namely time of day, car occupancy, and installation of an electronic transponder.; The last part of dissertation describes a simulation model to study the travel time profile before and after freeway expansion. The simulation model applies the earlier-mentioned scheduling choice model together with estimates from the empirical estimations. By considering scheduling and route choice by commuters, the time savings as well as the scheduling benefits from expanded road capacity can be measured. The results suggest that the benefits from letting commuters travel closer to their preferred schedules are comparable to time savings on a freeway with moderate congestion; the scheduling benefit increases faster than time savings when congestion worsens. (Abstract shortened by UMI.)...