A simple physical principle for the simulation of freeways with special lanes and priority vehicles

This paper presents a simple physical principle that can be used to solve the kinematic wave problem for freeways with special lanes and priority vehicles. The principle is shown to yield the flows for all possible ‘Riemann problems’ arising in a homogeneous highway, so that its application in a simulation is equivalent to the Godunov ‘classic’ finite difference approximation method. The principle is appealing because its physical basis, unlike purely mathematical formulae, suggests a natural way in which boundary conditions for practical problems may be treated. Perhaps the IT principle will prove useful for solving general problems, e.g. involving multicommodity networks. This issue deserves more study. As an illustration of this potential the paper shows that an IT simulation of the finite highway problem solved in the companion paper (Daganzo, Transportation Research B , 31 , 83–102, 1997) matches rather well the exact solution. Additional tests using other boundary conditions for the same problem also revealed a good match.