In a sub-area network, stop signs and signals at intersections can be a significant influence on travel paths. The presence of such devices often must be simulated in computerized highway networks so as to obtain more realistic assignments. One common way of doing this is to use "turn penalties." This is very resource-intensive, and has been known to confuse the path-building logic of some programs, resulting in poor assignments. An alternative method has been developed to avoid these problems. This method is based on theoretical models of delay, as a function of the v/c ratio of the controlled approach. Given the link's distance, the uncontrolled free speed, and the type of control device, a new "zero-volume" link speed and capacity are calculated to account for the delay induced by the control device. Further, the characteristics of the link are modified to account for delay caused by queuing: as traffic is assigned to the link, itsconstrained speed drops at a faster rate than if it had no control device. A county-wide travel demand model using this technique was implemented using minutp, and the control device simulation method was applied with a fortran program which modifies the speed and capacity of controlled links. A coparison of assigned volumes to ground counts by control device type showed reasonable results, and the constrained speeds on controlled links were also found acceptable. This paper appears in transportation research record no. 1283, Transportation systems planning and applications 1990.
Samenvatting