Drivers' perception of route alternatives as indicator for the indifference band

Although travel time is probably one of the most important attributes in route choice, the shortest time route is often not the preferred route, according to several studies in the literature. This study tries to explain this finding by testing the hypothesis that choice makers may be able to estimate travel times correctly for routes that they prefer but are biased against alternatives even if these are faster. For a few choice sets of routes in the city of Enschede, Netherlands, respondents were asked to choose a route and provide their estimated travel times for both the preferred and the alternative routes. These travel times were then compared with actual travel times from a license plate study. The comparison confirmed the hypothesis. For chosen routes, perceived travel times correspond quite well with actual travel times on average, whereas for routes not chosen, perceived travel times are overestimated by 3 to 4 min on average. These results show that drivers are not able or do not want to evaluate routes objectively. This finding implies that within an indifference band of route delay or travel time inequality of on average 3 to 4 min, drivers are probably not willing to alter their route choice, even if the traffic situation, induced, for example, by traffic management measures, changes in a negative way for their preferred route.