Outflow models based on velocity/density formulation used in dynamic traffic assignment

Outflow rate and link travel time have generally been surmised to be important attributes of intelligent transportation system (ITS). In this paper, two constant differential equation models are presented separately while inflow pattern is known. This is based on the velocity/density relation function given by Greenshields and the modified velocity/density relation function presented by Jakyakrishnan and Tsai. Considering the analytical solution of above constant differential equations cannot be acquired, its numerical solution is obtained by Runge-Kutta-Fehlberg algorithm. We also get the link travel time function basing upon the inflow and outflow patterns. The numerical simulation indicates that the outflow patterns, which are obtained respectively by the two outflow models, are almost approach the real traffic flow status according the traffic survey. However, the link travel time, which comes from the outflow model, which is based on modified velocity/density relation function, is more approach the real travel time.