Car following model by VISSIM
Vehicles are moving in the network using a traffic flow model. The
quality of the traffic flow model is essential for the quality of the
simulation. In contrast to simpler models in which a largely constant speed and
a deterministic car following logic are provided, (Fahrzustände
im Verkehrsflussmodell nach Wiedemann) . The basic concept of
this model is that the driver of a faster moving vehicle starts to decelerate as
he reaches his individual perception threshold to a slower moving vehicle. Since
he cannot exactly determine the speed of that vehicle, his speed will fall below
that vehicle’s speed until he starts to slightly accelerate again after reaching
another perception threshold. There is a slight and steady acceleration and
deceleration. The different driver behavior is taken into consideration with
distribution functions of the speed and distance behavior.
The car following model has been calibrated through multiple
measurements at the Institute of transport studies of the Karlsruhe Institute of
Technology (since 2009 KIT – Karlsruhe Institute of Technology), Germany. Recent
measurements ensure that changes in driving behavior and technical capabilities
of the vehicles are accounted for.
For multi-lane roadways a driver in the
- Technical specification of the vehicle, for example:
- Vehicle length
- Maximum speed
- Accelerating power
- Actual vehicle position in the network
- Actual speed and acceleration
- Behavior of driver-vehicle units, for example:
- Psycho-physical perception thresholds of the driver, e.g. ability to estimate, perception of security, willingness to take risk
- Driver memory
- Acceleration based on current speed and driver’s desired speed
- Interdependence of driver-vehicle units, for example:
- Reference to vehicles in front and trailing vehicles on own and adjacent lanes
- Reference to currently used network segment and next node
- Reference to next traffic signal
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