Calibration

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Introduction ​

This page is currently under development.

This section discusses common calibration items used for various facility types and how these items can be addressed in SwashSim.

Network calibration


 * link lengths
 * link horizontal curvature
 * grades
 * stop bar position
 * detector placement (for signal control)

Model calibration

Signalized intersections

Saturation flow rate: The saturation flow rates realized from a simulation are a function of the following factors:
 * Vehicle spacing within the queue: This is primarily a function of the 'stop gap' value, which is the distance left between the front bumper of a following vehicle and the rear bumper of its leader vehicle, when stopped in a queue. The default values are:
 * Small Auto - 8 ft
 * Large Auto - 8 ft
 * Small Truck - 13 ft
 * Large Truck - 18 ft
 * These values can be changed in the 'CarFollowModelParms.xml' file in the 'DataFiles_ModelParms' folder within the program folder. The vehicle type distribution will also impact the average stop gap values within any queue of vehicles.
 * Driver type distribution: Generally, a higher percentage of more aggressive drivers in the traffic stream will lead to higher saturation flow rates. The driver type percentages can be revised in the driver settings screen.
 * Vehicle acceleration: When accelerating from a stop, vehicles will initially accelerate at their desired acceleration rate. This value, however, may be overridden (i.e., made lower) by the car-following model or the maximum acceleration capability of the vehicle. By default, desired acceleration values are higher for more aggressive driver types. The desired acceleration multiplier values can be revised in the driver settings screen.
 * Car-following model parameters: The parameters of the car-following model will influence the acceleration of a following vehicle. Most of the vehicles behind the lead vehicle in the queue will spend the majority of their time during the queue discharge process in car-following mode. As mentioned above, the acceleration value calculated from the car-following model will override the desired acceleration when the vehicle is in car-following mode. The maximum acceleration of the vehicle might override the car-following acceleration value. This typically happens for large trucks on inclines. More detail about the car-following model can be found here.
 * Link free-flow speed: The free-flow speed of the link(s) downstream of the link where vehicles are queued will influence the speed to which vehicles will accelerate, which in turn can influence the queue discharge rate. Vehicle desired speeds are a function of the link free-flow speed and the driver type. The desired speed multiplier values can be revised in the driver settings screen.

Queue length: Stop-gap values, vehicle type distribution

Two-lane highways


 * Percentage split between passing and non-passing lanes in passing lane link
 * driver type distribution
 * percentage of driver types considered slower drivers