VS-NEMA Wizard

 

The VS NEMA Wizard is a tool for designing intersection controls. The intersections can have a maximum of four legs, pedestrian crossings and emergency vehicle preemption.

It takes seven steps for a controller design. The NEMA Wizard exports a set of parameters, which can be imported into any controller running VS-PLUS on it.

This is like Java: the programs and parameters (here: the NEMA Wizard export) are interpreted by the Virtual Machine (here: VS-PLUS).

Normally VS-PLUS is a programming environment of its own. The NEMA Wizard generates a VS-PLUS program which restricts itself to the NEMA standard.

The seven steps are the following:

  • Intersection: define the general intersection layout as the access roads and the main direction
  • Phases: define the detailed phases (left turns, through traffic, pedestrians, priority vehicles)
  • Overlaps: define the overlaps for right turns and pedestrian phases
  • Phasing sequence: define the phasing sequence (lead and lag)
  • Permissive periods: define the permissive periods (min, max and intergreen values)
  • Detectors: define the detectors, if any
  • Controller generation: generate the VS-PLUS control

The seven steps should be done in the mentioned order. It is always possible to jump back and forth to previous points.


Intersection


Intersection Window

Define here the general intersection layout as the access roads and the main direction. In addition you must define here which classes of traffic will be handled separately on the intersection.


Phases


Phases window, showing the phases for cars and pedestrians

Define here all phases of the intersection. According to the choice in the Intersection's Options box, up to two configuration pages can appear.

There is always a cars and peds configuration panel.

Preemption

Emergency vehicle preemption can be done with each of the defined access roads. There is no lane separation possible, i.e. an EVP call preempts the whole access road.

Numbering is from 21 to 24, starting with the main direction of the main street.


EVP phases definition


Overlaps

Overlaps are needed to define the behavior of all phases for individual traffic beyond the standard NEMA phases 1 to 8:

  • Pedestrians (phases 10, 12, 14 and 16),
  • Right turns (phases 17 to 20).

The panel consists of two main areas:

  • At the right side there is - pro memoriam - a complete layout of all IVT phases of the intersection.
  • At the left side there is the checkbox array in which the overlaps are defined. 

Check Box Array

The first row shows the 8 standard NEMA phases, phases 1 to 4 correspond to the first ring, phases 5 to 8 to the second.

The first column shows all phases which have to be assigned as overlaps: first the pedestrian phases, then the right turn phases.

In each column there is a number of checkboxes. If they are checked, the phases will go with the standard NEMA phase given in the column heading.


All overlaps for a complete four-legged intersection


Phasing sequence

Having defined phases and overlaps, the phasing sequence can be shown. There is not much to define, but to check if the resulting phase patterns correspond to what was intended.

  • On the upper half of the panel, each half ring can be set to lead or lag. At the same time the pattern resulting of the leading standard NEMA phase and all phases added to it as overlaps can be seen.
  • On the lower half of the panel the resulting phase patterns are shown. The sequence is read from left to right. If two possibilities are shown one above another, the controller might choose which one to use, according to the traffic situation.


Phasing sequence of a standard NEMA configuration


Permissive periods

This step is used for defining all timing and phase parameters. It consists of two sub-pages:

Timing

Use the timing sub-panel for basic parameters about a full cycle:

  • Cycle Time
  • Offset according to a central clock
  • Phase green for each standard NEMA phase from 1 to 8
  • Clearance time between each pair of phases.

All values are in seconds.


Permissive periods: timing window

Phase Parameter

The phase parameters define the timing details for each phase, including overlaps:


Permissive periods: phase parameter as list view

  • Standard Phases: the standard NEMA phases 1 to 8 as shown on the timing panel, using the IVT parameters
  • Pedestrians: the maximum four pedestrian overlaps, using the pedestrian parameters
  • Right Turns: the maximum four right turn overlaps, using the IVT parameters as well 


Detectors

This step is used for defining the detectors in the access roads.

Cars and Peds


Detectors for a standard intersection

 

 

Each access can have a detector. Clicking on the checkbox defines the detector or takes it away. 


Controller generation

This is the last step in defining a NEMA control using the VS NEMA Wizard.


Control paramerter generation options

Push the button; give the name of the CSV file and wait until "done" appears. The generation of the CSV file should take less than 1 second. The following generation of the VCE file takes a bit longer.

The CSV file contains all necessary parameters for further refinement in visual VS-PLUS or in VS-WorkSuite. In most cases such a refinement is not necessary and the VS-PLUS control data set (the VCE file) can be downloaded directly to the controller or to the simulation.