VISSIM使用指南

INTRODUCTORY TRAINING

VISSIM

VISSIM is a microscopic, time step and behavior based simulation model developed to model urban traffic and public transit operations. The program can analyze traffic and transit operations under constraints such as lane configuration, traffic composition, traffic signals, transit stops, etc., thus making it a useful tool for the evaluation of various alternatives based on transportation engineering and planning measures of effectiveness.

The traffic simulator in VISSIM is a microscopic traffic flow simulation model including the car following and lane change logic. VISSIM uses the psycho-physical driver behavior model developed by Wiedemann (1974). 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 afte r reaching another perception threshold. This results in an iterative process of acceleration and deceleration.

Open VISSIM and create a new file

For every transport network a separate VISSIM file is needed. To create a new network the following steps are to be followed.

1.Open the master plan of your study area as a background image

Building an accurate VISSIM model at least one scaled map that shows the real network. The image file of a digitized map (.jpg, .tiff, .bmp etc.) is to be imported as a background. This background can be displayed, moved and scaled in the VISSIM network window and is used to trace the VISSIM links and connectors.

2.Scale the background and save a scaled background.

Precise scaling is necessary for an accurate network model. A large scale distance (> 100 m / > 300 ft) is recommended to use.

3. Draw links and connectors for streets and junctions

The level of detail required for replicating the modeled transport network infrastructure depends on the purpose of a VISSIM application. While a rough outline of the analyzed intersection is sufficient for testing traffic actuated signal logic, a more detailed model is required for simulation analyses.

Link: The first step in coding a VISSIM network is to trace links. Each approach and section should be represented by one link. A link cannot

have multiple sections with a different number of lanes. Connectors (rather than links) should be used to model turning movements.

Connectors: In order to create a road network, links need to be connected to other links. It is not sufficient to place one link on top of another link in order for vehicles to continue on the other link. Instead, a connector needs to be created to connect the two links. Furthermore connectors are used to model turnings of junctions.

Set Parameters for the new file

1.Simulation Parameters

Traffic regulations: Specifies the standard driving side (For Ireland, Leftside-Traffic).

Simulation Resolution: The number of times the vehicle’s position will be calculated within one simulated second (range 1 to 10) (more than 3 recommended).

Random Seed: This parameter initializes the random number generator. Simulation runs with identical input files and random seeds generate identical results. Using a different random seed includes a stochastic variation of input flow arrival times.

2.Speed profiles