Overview
The second Strategic Highway Research Program (SHRP 2) Project C10B, Partnership to Develop an Integrated, Advanced Travel Demand Model with Fine-Grained, Time-Sensitive Networks: Sacramento-Area Application, is an important step in the evolution of travel modeling from an aggregate, trip-based approach to a completely dynamic, disaggregate methodology. In this project, an existing disaggregate activity-based model was integrated with an existing traffic simulation model to create a new, completely disaggregate model. At the same time that travel demand models have been evolving, traffic simulation models— which simulate the movements of vehicles through a highway network—have become more sophisticated due to improvements in computing. The product of SHRP 2 Project C10B is an integrated model that simulates individuals’ activity patterns and travel and their vehicle and transit trips as they move on a real-time basis through the transportation system. It produces a true regional simulation of the travel within a region, for the first time using individually simulated travel patterns as input rather than aggregate trip tables to which temporal and spatial distributions have been applied to create synthetic patterns. A unique feature of this model is the simulation of transit vehicles as well as individual person tours using transit. The new integrated model has been developed and implemented for the entire Sacramento, California, region. The integrated model components include (1) SACSIM, the regional travel model maintained by the Sacramento Area Council of Governments (SACOG), the regional metropolitan planning organization (MPO), and (2) DynusT, a mesoscopic traffic simulation model developed by the University of Arizona. SACSIM includes an activity-based demand model, Day-Sim. The transit simulation is performed by FAST-TrIPs (Flexible Assignment and Simulation Tool for Transit and Intermodal Passengers), also developed by the University of Arizona. The integrated model also includes the ability to run MOVES (Motor Vehicle Emission Simulator), the air-quality analysis program developed by the U.S. Environmental Protection Agency (EPA).