INTEGRATED OPERATIONS OF SURFACE STREET AND FREEWAY SYSTEMS

This paper presents a study on integrated operations of surface street system and freeway system using VISSIM, a microscopic simulation model. A traffic network consisting of a surface street and a freeway segment was constructed in VISSIM. The surface street and freeway are connected through a diamond interchange with on-ramps and off-ramps. However, the traffic flow patterns and traffic demands were manipulated manually for the purpose of testing the effectiveness of various system integration strategies. Primarily, integration of the two systems was achieved through coordination of the interchange signals with the ramp-metering signal. The signal control logic was programmed using VISSIM's Vehicle Actuated Programming (VAP), which serves as an external control function for the simulation model. The features of dynamic ramp metering and traffic responsive signal timing were implemented in the simulation model. The system control was programmed to react to freeway incidents and temporary traffic demand variations to achieve optimized operations for the entire system. The effectiveness of the integrated operations was documented based on the results from simulation. Testing of the proposed integration strategies indicated improved operations on both the surface street and freeway systems.