Car Following

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The car-following model is used to calculate an acceleration value for a vehicle in a follower mode. SwashSim employs the Modified-Pitt car-following model (Cohen, 2002a and 2002b). The Modified-Pitt car-following model has been demonstrated (Cohen, 2002a and 2002b; Washburn and Cruz-Casas, 2007) to work well for multiple traffic flow regimes (e.g., uninterrupted flow and queue arrival/discharge flow). The Modified-Pitt car-following equation calculates the acceleration value for a trailing vehicle based on intuitive parameters such as the speed and acceleration of the lead vehicle, the speed of the trailing vehicle, the relative position of the lead and trail vehicles, as well as a desired headway. This equation also incorporates a sensitivity factor, K, which is discussed in the next subsection. This equation allows for relatively easy calibration. Car-following models are generally based on a ‘driving rule’, such as a desired following distance or following headway. The Modified-Pitt model is based on the rule of a desired following headway. The main form of the model is as follows.

$$ {a_f}(t + T) = \frac\ $$

where