This paper studies a control of traffic flow dynamics in urban road networks. The signal control system of the congestion length is described by a nonlinear time-varying discrete dynamic system and synthesized by using the hierarchical control. A signal control algorithm in which the three signal control parameters consisting of the cycle length, green split and offset are searched systematically so as to minimize the sum of congestion lengths in the urban road network is presented. The dynamic route guidance system is consisted of both the evaluation for the mean OD travel time and the route search algorithm. The traffic flow control system, which is most effective to reduce the congestion lengths in urban road networks, is designed by connecting the signal control system with the dynamic route guidance system in real time.