VISSIM 5.30-05 User Manual

7 Simulation of Pedestrians
► tau (τ)
Tau is the relaxation time, which one can relate to a reaction time or
inertia, as it couples the difference between the desired speed and
direction v_0 and the current speed and direction v to the acceleration a:
a = (v_0 – v) / τ.
In the folder ..EXAMPLES\TRAINING\PEDESTRIANS\PARAMETER
DEMONSTRATION you can find training example models specifically
demonstrating the effect of this parameter.
► lambda_mean (λ_mean)
Lambda governs the amount of anisotropy of the forces from the fact that
events and phenomena in the back of a pedestrian do not influence him
(psychologically and socially) as much as if they were in his sight. From
lambda and the angle φ between the current direction of an agent and
the source of a force a factor w for all social (i.e. non-physical) forces is
calculated that suppresses the force, if φ ≠ 0 and λ < 1: w(λ) =
( λ + ( 1 – λ ) ( 1 + cos(φ) ) / 2 ). So, if φ = 0 one has w = 1 and if φ = π
one has w(λ) = λ.
In the folder ..\EXAMPLES\TRAINING\PEDESTRIANS\PARAMETER
DEMONSTRATION you can find training example models specifically
demonstrating the effect of this parameter.
► A_soc_isotropic and B_soc_isotropic
These two parameters together with λ govern one of two forces between
pedestrians:
F = A_soc_isotropic w(λ) exp(-d/B_soc_isotropic) n, with d as distance
between the pedestrians (body surface to body surface) and n as unit
vector pointing from one to the other.
► A_soc_mean, B_soc_mean, and VD
These parameters determine strength (A) and range (B) of the social
force between two pedestrians. The social force between two
pedestrians is calculated as F = w(λ) A exp(-d/B) n, if the influencing is in
front (180°) of the influenced pedestrian, else it is zero. Here w(λ) is the
factor calculated from λ, which is explained above, d is the distance
(body surface to body surface) between two pedestrians and n is the
unity vector pointing from the influencing to the influenced pedestrian.
Note that if the parameter VD is greater than zero the relative velocities
of the pedestrians are considered in addition.
In this case the distance d is generalized to and thus replaced by
d -> 0.5 sqrt( (d + |(d – (v_1 – v_0) |VD)² - |(v_1 – v_0) VD|²)
with VD given in [seconds]. Here v_0 is the velocity of the influenced and
v_1 the velocity of the influencing pedestrian and d points from the
influencing to the influenced pedestrian with |d| = d. (The “influenced
pedestrian” is the one for whom the force is calculated.)
In the folder ..\EXAMPLES\TRAINING\PEDESTRIANS\PARAMETER
DEMONSTRATION you can find training example models specifically
demonstrating the effect of parameter VD.
430 VISSIM 5.30-05 © PTV AG 2011