Assessment of Various Methods of Designing & Coordinating Ramp Metering & Variable Speed Limit for Highway Traffic Management

Urban highways are one of the infrastructural facilities that have an important role in daily transportation. Proper management of traffic using the highway controllers would lead to a uniform flow that is very effective in reducing the delays and increasing the flow capacity. Studies have been conducted on the effectiveness of these controllers on flow and this is becoming one of the important debates in the field of traffic management. Hence, in this paper, the procedures and methodologies used for designing and coordinating ramp metering and variable speed limit are generally classified and presented. Then by evaluating the results obtained from the implementation of each method, a qualitative and comprehensive comparison between them is presented. As a comparison result, it is understood that ramp metering is effective only when there is little congestion on the main road. Influence of ramp metering decreases when congestion increases. In this case, applying the variable speed limit at the upstream of the onramp would help to make the traffic flow uniform. Using RM and VSL simultaneously, RM reaches maximum efficiency on the main road traffic flow.