Drivers' ability to detect changes in timing at signalized intersections

Drivers have limited awareness of changes in trip attributes or the performance of the traffic system. Due to non-utilitarian behavior and perceptual biases a distinctive amount of changes go unnoticed or are valued incorrectly, which makes drivers indifferent to changing traffic conditions to a certain extent. Defining the indifference band and understanding the probability of behavioral response to changes is valuable input for road operators and traffic engineers designing traffic management measures. To explore the thresholds of the indifference band, a field study was conducted. The study focused on the ability of drivers to observe and rightly value differences in the timing of traffic lights, in particular where the length of the red phase is concerned. Results confirm that drivers have limited awareness of differences in the length of the red phase of traffic lights, both in absolute and relative sense. Moreover, a large range of waiting times are perceived by drivers as being close to the average waiting time, which offers some insight in the indifference band. However, if the reason for waiting is not intuitive the perception of drivers becomes more accurate and their awareness increases (indifference band narrows).