Pacific Southwest Region 9 UTC

Get More Out of Variable Speed Limit Control: An Integrated Approach to Manage Traffic Corridors with Multiple Bottlenecks

Project Number


Project Summary

Variable speed limit (VSL) has been studied as a variable control method to improve traffic safety under various conditions. Most existing studies have not investigated how to leverage VSL to increase traffic throughput or reduce environmental costs induced by congestion spillbacks. In this research, we explore the feasibility of using an integrated VSL framework to enhance the traffic performance in terms of traffic throughput and environmental costs. We will use the state-of-the-art traffic flow model and real-time traffic data to identify bottlenecks, estimate spillover effects without control, and design integrated VSL and ramp metering strategies to reduce or eliminate shockwaves emanated from the bottlenecks. Unlike previous VSL control where the primary objective was to smooth traffic speed, our approach targets several goals: reduce speed variation, increase throughput, and reduce emissions and fuel use. We will implement the VSL control strategies using macro emission rates from Motor Vehicle Emission Simulator (MOVES) to investigate the impact of different levels of data availability and drivers’ compliance rates. From the simulation tests, we will also investigate the feasibility of inserting probe vehicles on certain corridor segments, to improve data accuracy and provide guiding speed to enhance the VSL control efficiency simultaneously.

Project Status

In progress



Topic Area

Urban Mobility

P.I. Name & Address

Professor, Department of Civil and Environmental Engineering
UC Davis

Funding Source: USDOT

Funding Amount: $116,813

Start and End Dates: October 1, 2018 to September 30, 2019