The integration of urban traffic control and dynamic route guidance: The role of dynamic assignment

The Integration of Urban Traffic Control (UTC) and Dynamic Route Guidance (DRG) is examined in the context of systems developed by Siemens, namely EUROSCOUT and UTC which is based on programmable signal controllers and traffic computers. The potential for exchanging inputs between the two systems so as to improve the quantity and quality of the traffic information available to each is described. As the number of in-vehicle route guidance units increases, problems can arise with all-or-nothing route recommendations. In urban networks operating close to capacity, all-or-nothing routeing may generate some new congestion as guided vehicles are routed away from existing congestion. Multi-routeing is required in conjunction with a dynamic assignment model. The paper sets out a functional specification for such an assignment model. As inputs, the dynamic assignment model will require link travel time functions and matrices of Origin-Destination (O-D) demands. The link travel time functions should take into account not only the flow into each link but also the effect, through demand-responsive signal control, of cross flows on the capacity of each link exit. It is suggested that recursive least squares may be used to estimate the parameters of link travel time functions on the basis of data from DRG and UTC.