User-Optimal and System-Optimal Route Choices for a Large Road Network

Solutions to the route choice problem for assumptions of user-optimality and system-optimality are presented for the road network of the Chicago region. Regionwide results show a 5% decrease in total travel time would be achieved during the morning peak period, if a system-optimal solution based on travel times were implemented. Among the costs of this solution is a 1.5% increase in vehicle-miles traveled. Findings for differences in link flows and individual origin-destination pairs complete the paper.