ROUTE CHOICE AND ADVANCED TRAVELER INFORMATION-SYSTEMS ON A CAPACITATED AND DYNAMIC NETWORK

Much of the push behind Intelligent Transportation Systems (ITS) has c ome from the hope that providing travelers with better information wil l result in reduced travel time and traffic congestion. Phase 1 of the United States' IVHS National System Architecture project, for instanc e, made ATIS (Advanced Traveler Information Systems) the centerpiece o f its benefits evaluation, and ATIS has been the subject of numerous t raffic simulation studies. The objective of this paper is to examine t he 'informational' assumptions embedded in traffic simulations, and to assess how these assumptions affect simulation results. Most importan tly, this paper examines the hypothesis that increasing market penetra tion can lead to a decrement in network performance. The paper proves, for a simple parallel network, that increasing the market penetration of accurate information cannot harm network performance. For this sam e network, the paper shows that increasing the penetration of instanta neous travel time estimates might degrade network performance. The pap er also asserts that the existence, or non-existence, of an optimal ma rket penetration is moot. The suggestion is that ATIS should not be vi ewed as a strategy for achieving system optimal traffic distributions. ATIS should instead be viewed first as a service to the public, to im prove their confidence and comfort in using the system, and second as a means for steering traffic away from dis-equilibrium behavior and to ward user optima that utilize alternate routes where feasible. Copyrig ht (C) 1996 Elsevier Science Ltd