Online Traveler Information in Stochastic Dynamic Networks

This paper establishes a general framework to study the effects of online information on users´ routing decisions and the system cost in a stochastic dynamic traffic network under a generalized equilibrium condition. Users make adaptive routing decisions, and the rule that maps a user´s current state, including node, time and information, to a decision on the next node to take is defined as a routing policy. This definition allows for a wide variety of information accessibility situations, thus excluding the usually simplified assumptions such as either no information or full information. A user´s choice set contains routing policies, rather than simple paths. A user equilibrium is reached when each user follows a routing policy with minimum perceived disutility at his/her departure time and no user can unilaterally change routing policies to improve his/her perceived disutility. Computational tests are carried out in a hypothetical network, where random incidents are the source of stochasticity. System costs derived from four models with different information accessibility situations are compared. The adaptiveness to online information leads to travel time savings at equilibrium. As a byproduct, travel time reliability is also enhanced. The value of online information is an increasing function of the incident probability. Travel time savings are high when market penetrations are low. However, the function of travel time saving against market penetration is not monotonic