CONGESTION, FLOW AND CAPACITY. HIGHWAY CAPACITY AND LEVEL OF SERVICE. PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON HIGHWAY CAPACITY, KARLSRUHE, GERMANY, 24-27 JULY 1991

A new model reflecting the relationships between congestion, flow and capacity is presented. The two concepts of capacity are dealt with in this model: one is the output capacity of a length-limited link or road in traffic systems, which is the same meaning as the capacity usually adopted in the Highway Capacity Manual; another is the carrying capacity of the link. Both of the two capacities influence traffic congestion: the finiteness of the output capacity is a critical factor for causing congestion; the carrying capacity affects the time evolution of traffic congestion on such a link. Through analysing the new model, one may find that the time evolution of traffic congestion on a link can exhibit an extraordinarily rich spectrum of dynamic behavior, from stable states, to regular oscillations, to apparently random fluctuations--chaotic behavior. This implies that there can be complicated patterns in traffic flow under congested conditions.