This video shows a VISSIM microsimulation of traffic flows at a toll plaza. The basic model was built to analyze traffic operations at the Benjamin Franklin Toll Plaza in Camden, New Jersey, USA. VISSIM was used to simulate the existing conditions and future scenarios and to evaluate the vehicle delays and throughput at the toll plaza.
The original model has been enhanced to show how scripting through the VISSIM COM interface can be used to further optimize the gate allocation and queue selection. It considers 3 main vehicle classes (cars, HGVs and buses) and allows for various payment methods which are indicated by the vehicle’s color: EZ-Pass vehicles (green), Cash Pay vehicles (light blue), Card pay vehicles (dark blue) and Violators (red).
The scripting was done using VBA (Visual Basic for Applications) inside Microsoft Excel. A user interface was implemented to easily control the toll plaza during a simulation run with the following features:
1. Free user-definable allocation of all gate attributes in Excel, both before and during a simulation run.
2. Automatic best gate selection based on the settings defined for each gate (in Excel): For each approaching vehicle an optimum gate is determined according to its vehicle class, payment method and approach lane on the main road.
3. The current queue length can be displayed in Excel and/or in VISSIM. For realistic gate selections these queue lengths also include those vehicles that are assigned to a certain gate even if they are not queuing yet.
4. Optional automatic adjustment of gate openings according to current traffic conditions: If a defined queue length threshold is reached for a number of gates, additional gates will open. If the queues are short, some gates will be closed.
As with every traffic model, some restrictions apply, especially due to the fact that here are many decision options and vehicle interactions within short range. Among these restrictions are some unrealistic drive paths during low traffic (due to the lane configurations) or a delayed reaction to gate openings/closures as lane assignments take place well in advance of the gates.
The gain from this model however is a realistic dynamic microsimulation of the traffic at a toll plaza with highly configurable gate configurations. It also provides a robust test site to evaluate various sophisticated gate management strategies against traffic flow and vehicle mix.
Post time: May-07-2017