Road Traffic Congestion and Public Information:An Experimental Investigation

This paper reports two laboratory studies designed to study the impact of public informationabout past departure rates on congestion levels and travel costs. Our experimental design isbased on a discrete version of Arnott, de Palma, and Lindsey’s (1990) bottleneck model wheresubjects have to choose their departure time in order to reach a common destination. Experimentaltreatments in our first study differ in terms of the level of public information on past departurerates and the relative cost of delay. In all treatments, congestion occurs and the observed totaltravel costs match the predicted ones. In other words, subjects’ capacity to coordinate is neitheraffected by the availability of public information on past departure rates nor by the relative costof delay. This absence of treatment effects is confirmed by our finding that a parameter-freereinforcement learning model best characterizes individual behavior. The number of experimentalsubjects taking the role of drivers is four times larger in our second study than in our first study.We observe that subjects’ capacity to coordinate is not affected by the size of the population.