Coordinated Control Signal Input Strategies for Freeways

Abstract

Strategies for inputting coordinated control signals in a freeway system are studied. Based on the symmetric, two-lane Nagel-Schreckenberg (STNS) model, a cellular automaton model of a coordinated control section on a freeway with only one on-ramp segment and a mainline segment is established with access to real-time traffic information from an intelligent transportation system (ITS). The characteristics of traffic flow obtained by inputting coordinated control signals in the controlled section are discussed based on the results of simulations conducted using different control strategies. The effects of various traffic states, mainline upstream traffic volumes, and ramp demands on actual road capacity and traffic flow are analyzed by inputting no control signal, only on-ramp control signal, only variable speed limits signal, and speed limits, and ramp-metering signal. The simulation results indicate the following: (1) the applicability of coordinated control as a main traffic management tool is better than that of other control methods; (2) the goal of decreasing the vehicle passing time, suppressing traffic jams; (3) and enhancing road actual traffic volume can be realized by using the strategy of inputting different control signals under different traffic demands.