When the Field Is Not Enough: Using Complementary Field and Lab Experiments to Investigate Congestion Pricing Responses

We use data from a field experiment collecting route choices using GPS recorders and a lab experiment eliciting risk attitude characteristics of drivers. We find that drivers behave in predicted ways in response to variations in average travel times, and in response to manipulations of route pricing. Demand functions are downward sloping in tolls and in travel times. We do not find that drivers respond to variations in the unreliability of travel times, but this is not due to their risk attitudes. Almost all drivers are risk averse, and express a revealed preference in favor of the relatively safe route that is increasing in risk aversion. Because the alternate routes are located at some distance apart, we suspect that the lack of response to travel time unreliability is to be found in biases in drivers expectations of unreliability.