Overview
The main objective of SHRP2 L04 - Incorporating Reliability Performance Measures in Operations and Planning Modeling Tools, is to develop the capability to produce reliability performance measures as output from planning and simulation models. The project is divided into three phases. Phase I (report dated June 2010) presented a review of the state of the art and the practice with regard to the use of the concept of reliability, and proposed a framework and functional requirements for the inclusion of travel time reliability estimates in transportation network modeling tools. The proposed framework for generating reliability-related output is designed to be nearly independent of the modeling resolution (micro-, meso-, or macro-scopic models). Measures of reliability include travel time distributions, delay probabilities, and reliability proxies. Phase II, currently underway, involves testing and demonstration of the framework as well as the development of guidelines for incorporating travel time reliability into traffic simulation models. Phase III, also underway, addresses how a feedback mechanism could incorporate reliability into travel demand forecasting models. At the heart of the approach is a focus on measures of travel time variation. The research demonstrates the process for simulating travel time distributions in response to factors that cause both demand variation (special events, variation in individual driver behavior, use of alternative modes) and supply variation (weather, work zones, incidents, variation in individual driver behavior, traffic control, dynamic pricing) at the regional and corridor levels.