Some Theoretical Aspects on Optimal Toll-Rate and Scale of Urban Expressway

In this paper, the optimal toll-rate and scale of urban expressway is discussed economically. The criterion used is the total surplus of expressway, which is defined as the sum of consumer's surplus of expressway users and producer's surplus on the side of expressway administrator. The total surplus is equivalent to the difference of the value of total saved travel times of expressway users and the total cost required to construct and administrate expressway systems. The flow-dependent travel times is assumed, and traffic demand is induced through equilibrium method. On the other hand, for the management of expressway to be capable, the accounting condition that the fare revenue must repay the total cost should be satisfied. Under this accounting condition, the optimal rate and scale which maximize the total surplus are requested, and their properties are examined. The analysis is practiced for both caces of flowindependent cost function and flow-dependent cost function. One remarkable result is that the maximum feasible scale under the accounting condition does not privide a maximum for total surplus.