The Effect of Using Variable Speed Limit System on Transportation Efficiency in Highways

Improving operational efficiency and safety on freeway segments has long been recognized as a priority in traffic communities. The variable speed limit (VSL) has received increasing attention and is recognized as one of the most promising tools to manage traffic flows in freeway. Because of its ability to properly respond to real-time traffic fluctuations, VSL control has shown that it can replace conventional static speed limit strategies. The VSL was initially designed to reduce speed differences and harmonize traffic flow on hazardous freeway segments, to lower rear-end collision rates, and to improve traffic safety.

This study used data collected from Qom-Tehran freeway for its case study, according to the driver behavioral parameters in Iran to evaluate the effectiveness of the proposed VSL control system by AIMSUN.

Considering the speed of 70 km/h as the maximum speed at kilometre 5 by the VSL, due to blockage in the upstream, there is a 4-hour reduction in vehicles total travel time over the modeling period. In other words, based on the simulation results (single VSL), the Delay, Stop, Travel time and Pollutant Production Respectively was fell by 3.5%, 19%, 1.5% and 1.5%.

Using VSL system in accident prone routes has positive effects on the indicators of Latency, Travel time, Stops and Pollutant emissions. As increasing productivity is important in all systems, it can be seen that the using this system in accident prone routes is very important to increase safety and improve the route performance due to reducing Travel time, Fuel consumption, Secondary accidents and Pollutant emissions.