Robust Design, Analysis and Evaluation of Variable Speed Limit Control in a Connected Environment with Uncertainties

Connected vehicles via vehicle to vehicle (V2V), as well as vehicle to infrastructure (V2I), communications will open the way to manage and control traffic in a much more effective way than in today’s traffic where sensing and control actions are very limited. While vehicle technologies are progressing quickly, it is just a matter of time until infrastructure will follow and provide the necessary instrumentation for V2I communication. The technology of V2I has been around for several decades and has been tested in automatic toll collection and other applications.

One of the main remaining issues is the cost of investment and decision making. In order to properly evaluate cost, however; stakeholders need to understand the potential benefits. V2I technologies will allow for effective ways of dealing with incidents, controlling traffic flow, and routing vehicles away from congested areas. Control techniques for traffic flow include variable speed limit (VSL), lane change control, ramp metering, etc. This project will focus on VSL systems that are practical and whose performance can be established analytically and in simulations. 

Despite considerable research in the area of VSL control and the deployment of such technology in various places, the full potential benefits of VSL as reported in literature are controversial and often conflicting. The lack of consistency in the benefits of VSL may be attributed to various factors, including the following: accuracy of the models used, lack of robustness of the VSL controllers developed in a way that a small disturbance may lead to considerable deterioration of performance, lack of rigorous analysis to support and explain simulation results, and others.

The purpose of this project is to address the issue of robustness in the design of VSL and bring such schemes closer to a successful implementation with consistent and well-understood benefits. The researchers plan to use a traffic flow model that incorporates modeling uncertainties in terms of unmeasured unknown disturbances, parametric uncertainties in the various parameters of the model, density and flow measurement noise and uncertainties in the assumed fundamental diagram. With a more realistic model, the team plans to analyze its open loop properties to be consistent with what the researchers observe in practice (qualitatively, at least) and from microscopic simulations (more quantitatively). The team then plans to use this understanding to design robust VSL (RVSL) schemes which will maintain acceptable performance in the presence of uncertainties. Unlike most of the work in the area of VSL, the researchers approach is to rigorously analyze all properties of the RVSL under different initial density conditions and varying demands, as well as different uncertainties. Rigorous analysis is something that is missing in most of the work on VSL, which often rely solely on simulations to show benefits.

As a result, it is difficult to understand inconsistencies and differences in results published by different researchers. In addition to analysis, the researchers plan to demonstrate our analytical results and benefits of the designed RVSL schemes using first macroscopic, and then more realistic microscopic, simulation models of the traffic on I-710 where the relative volume of trucks is high; thus introducing more uncertainties in the macroscopic model (under different levels of demands and incidents). The EPA model, Motor Vehicle Emission Simulator (MOVES), will be used to evaluate the emissions and impact on environment with RVSL and without.

Research Area