VISSIM 5.30-05 User Manual

5 Base Data for Simulation
Because of the combination of psychological aspects and physiological
restrictions of the driver’s perception, the model is called a psycho-physical
car-following model.
The following sections describe the various behavior parameters in VISSIM.
5.4.2 Car Following Behavior
These parameters are available:
● The Look ahead distance defines the distance that a vehicle can see
forward in order to react to other vehicles either in front or to the side of it
(within the same link). This parameter is in addition to the number of
Observed Vehicles.
- The min. value is important when modeling lateral vehicle behavior.
Especially if several vehicles can queue next to each other (e.g.
bikes) this value needs to be increased. The value depends on the
approach speed. In urban areas it could be 20-30m (60-100 ft).
- The max. value is the maximum distance allowed for looking ahead.
It needs to be extended only in rare occasions (e.g. for modeling
railways if signals and stations are to be recognized in time)
Without increasing the min. look ahead distance while modeling lateral
behavior it may happen that vehicles do not stop for red lights or for each
other. The Number of Observed Vehicles (by default: 4 for Urban driving
behavior, else 2) should not be changed to compensate for this behavior as
it might easily result in unrealistic behavior elsewhere.
130 VISSIM 5.30-05 © PTV AG 2011