Route Guidance Algorithms Effective for All Levels of Take-Up and Congestion.

This paper describes work carried out under the EC `DRIVE' programme, the aim being to develop route guidance strategies which direct users to multiple routes between each origin-destination pair, and thereby provide stable and effective guidance even when a large proportion of drivers are guided. A model is proposed in which guided and unguided drivers have different route choice assumptions, but are still able to interact with one another; the guidance may be based on either user or system objectives. Conditions are deduced under which the resulting route pattern is guaranteed to exist and be stable. To assess the performance of the strategies, simulations are carried out on two real-life networks, for a number of different demand levels, levels of equipped vehicles, levels of error in (or adherence to) the guidance recommendations, and different guidance criteria. The simulations are extended, in order to examine firstly the influence of behaviour of unguided drivers on the benefits obtained, and secondly the performance of the strategies in cases of unforeseen variations in network conditions. Finally, some comparisons are drawn with a route guidance strategy developed in a parallel `DRIVE' project, where only one route is recommended per origin-destination pair.