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TRANSIMS
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TRANSIMS FUNDAMENTALS

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ADDITIONAL TRANSIMS INFORMATION

TRANSIMS

Travel Modeling Procedures

TRANSIMS simulates the second-by-second movement of persons and vehicles throughout a region. A simple set of rules is used to govern vehicle movement. A 7.5-meter grid describes vehicle location. This grid results in rough instantaneous speed estimates for individual vehicles however average link speeds are estimated reasonably well for time intervals as short as 15 minutes. The time varying data from the Microsimulator provides a more accurate representation of queuing and congestion over the course of an entire day compared to methods used for typical static equilibrium assignment models.

TRANSIMS does not simulate complex driver behaviors, detailed pedestrian movements, or precise intersection operations. Exacting operational analyses of highway facilities, including simulation of advanced traffic control technologies, are more appropriate for sub-area application of highly specialized traffic simulation models.

Recent applications of TRANSIMS are purposefully drawn from 4-step travel demand models. Person-travel needs have been estimated with trip-based and tour-based models. Travel destinations and modes are modeled with nested choice methods currently used in practice. Iterative feedback is used to refine travel choices. However, the significant differences derive from modeling individual travel choices and simulating these choices using internally consistent definitions of time and personal travel schedules.

The move from aggregate, parameter-driven methods to agent-based, rule-driven methods pre-dates TRANSIMS and has been a long while in the making. Regional microsimulation adds a key strategic capability to the study of travel and transportation. Improved service information for individual travelers allows for better modeling of travel scheduling and peak spreading phenomena. Better speed and acceleration estimates support more detailed congestion, fuel, emission, and safety analyses. The technology embodied in TRANSIMS gives planners and decision-makers an ability to consider transportation issues and prospective solutions in greater depth than ever before.