Mean Driver Reaction Time in Paramics

UPDATED: April 12, 2017

Mean Driver Reaction Time (MDRT) is an attribute representative of the PIEV time (Perception-Identification-Emotion-Volition) of a driver. The basis of car following theory is that the PIEV time is the time that it takes for a following driver to perceive a change to the leading vehicles speed/behaviour, identify the change, emotionally react to the change and then to implement a driving decision based on the change in behaviour/speed.

The PIEV time is closely associated with the shockwave phenomenon associated with traffic flow theory in which a driver’s late reaction to the leading vehicle causes their overreaction. This in turn causes a late reaction of subsequent vehicles, creating a shockwave effect in high flow conditions were vehicles are traveling in minimum headway conditions.

A following vehicle will react to the speed the lead vehicle is traveling lagged by the MDRT. For example the MDRT is 0.9 seconds and a leading vehicle decelerates, it will be 0.9 seconds before the following vehicle reacts to the lead vehicles change in speed. This is true for both acceleration and deceleration.

The default value of 1 second has been validated in studies throughout the initial Paramics development, however it is recognized that there are very different traffic flow conditions worldwide and it is recommended that the default value be used as an initial value and then altered as part of the calibration process if required.

The MDRT is set at a global level in the Core Network Attributes>>Advanced>>Core>Mean Driver Reaction Time and the Editor Palette>>Link>>Behaviour>>Reaction Factor. The MDRT applied to an individual vehicle is a product of both factors.


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