VISSIM 5.30-05 User Manual

5 Base Data for Simulation
The vehicle brakes if it cannot pass the signal head within 2 seconds
when continuing at its current speed rate.
In the range in-between, if both options applied, a normally
distributed random variable decides whether the vehicle brakes.
- One Decision: The probability p of the driver stopping at amber light
is calculated using a logistic regression function with the current
speed v and the distance from the vehicle front to the stop line dx as
independent variables and three fitting parameters (Alpha, Beta 1,
Beta 2):
p =
1+
e
1
−α
−β
1v−
β 2dx
The provided standard parameter values have been derived from
empirical data.
Enter the appropriate probability factors.
A decision is kept until the vehicle has passed the stop line.
The option One Decision will produce the most accurate results if the
number of Observed vehicles is increased accordingly (see [FOLLOWING]).
This is due to the fact that a signal head internally is modeled as a vehicle
and will only be recognized if the number of vehicles and network elements
in front of the signal head does not exceed the value resulting from number
of Observed vehicles minus 1.
Applied deceleration
Once the driver has decided to stop according to the decision model, a
constant deceleration rate will be calculated for the target braking to the
stop line, cf.section 5.1.
The applied deceleration rate bapplied depends on the distance to the stop
line dx and the current vehicle speed v and is calculated as follows:
Where brequired is the required deceleration and bmax is the maximum
possible deceleration according to the defined deceleration function.
142 VISSIM 5.30-05 © PTV AG 2011