Incorporating weather impacts in traffic estimation and prediction systems

Traffic Estimation and Prediction Systems (or TrEPS) are some of the tools currently available for traffic managers and operators to assist with evaluating and implementing transportation advisory, control and treatment strategies, including those that mitigate weather impacts. TrEPS predict where and when drivers travel on the road network, and enable dynamic control and traffic management systems to anticipate problems before they occur, rather than simply reacting to existing conditions. As part of a Dynamic Traffic Assignment (DTA) research project that began in 1994, the FHWA Research and Development Program developed two TrEPS: (1) DYNASMART-P is an off-line system that supports transportation network planning and traffic operations decision-making, and (2) DYNASMART-X which is a real-time system that interacts continuously with loop detectors, roadside sensors and vehicle probes, providing realtime estimates of traffic conditions, network flow patterns and routing information. Significant improvements in traffic estimation/prediction capabilities and overall utilities of these systems for traffic management can be achieved by upgrading or adjusting them to account for the impacts of weather. This paper summarizes the results of a study sponsored by the FHWA Road Weather Management Program to develop weather-sensitive traffic prediction and estimation models and incorporate them in existing TrEPS. The study included a review of existing knowledge on traffic responses to weather conditions and the application of weather-responsive advisory and control strategies. Recognizing the deficiency in current practice, we develop traffic estimation and prediction models at the corridor and network levels that account for traffic response to inclement weather with and without the presence of advisory and control strategies and incorporate these models in existing TrEPS.