Delays caused by a queue at a freeway exit ramp

We consider here what happens to traffic on a freeway when a queue from an exit ramp backs onto the freeway causing a partial blockage of the right lane. Exiting vehicles are confined to the right lane but through vehicles can travel in any lane. The two vehicle types interact but their queues must be treated separately. This illustrates a special case of a model of ‘freeways with special lanes’ formulated by Daganzo. Whereas Daganzo presented a numerical scheme of calculating flows, the emphasis here is on graphical evaluation of the complete evolution of the queues. The graphical solution more clearly illustrates the practical issues, at least in this special situation.