TRANSIMS is one part of the multi-track Travel Model Improvement Program sponsored by the U.S. Department of Transportation, Environmental Protection Agency, and Department of Energy with the purpose of developing new, integrated transportation and air quality forecasting procedures necessary to satisfy the Intermodal Surface Transportation Efficiency Act and the Clean Air Act and its amendments.

TRANSIMS is a set of integrated analytical and simulation models and supporting databases. The base set of technologies includes modules to develop a synthetic population, activity list, and to route travelers between activities to simulate second-by-second movements on a transportation infrastructure. Feedback methods for stabilizing the simulation and for modeling some of the transportation characteristics are fundamental elements of the TRANSIMS framework.

The TRANSIMS framework simulates the daily activities and movements of individuals in an urban region. The individuals are synthetic—they do not represent specific people—but are statistically indistinguishable from the actual census. Conversely, the locations visited by individuals are real street addresses that reflect actual land-use patterns in a region.

TRANSIMS provides the following information about the synthetic population and its mobility:

• Household structure and demographics
• Activity locations, times, and durations
• The number of trips between activities, including route plans and execution of the route plans in the transportation network