VTC Regions Guide

This guide will show you how to configure regions in order to classify turns/link movements (left, right, through). There are two main concepts:

  1. The “Region of Interest” (ROI): This outline should include the area of video that contains traffic to be counted. The purpose of the ROI is to exclude areas of the image from processing (for example, traffic which is not desired to be counted).

  2. Approach and Exit regions: Each pair of approach/exit regions (for example, Approach 1 and Exit 1) originates from one road. The Approach and Exit numbering is based on a 4-way intersection; the approaches are numbered in counterclockwise order. A typical 4-way intersection will have four Approaches and four Exits. The purpose of the Approaches and Exits is to determine which road a vehicle appeared and exited on. This is used to classify the movement.

VTC can be configured for junctions other than 4-way intersections. To configure a two-way road without any junction, set one direction as Approach1/Exit1 and the opposite direction as Approach3/Exit3. Configuring Approach2/Exit2 and Approach4/Exit4 is also acceptable.

Drawing a Region Shape

Click any Approach or Exit button in order to begin drawing. Draw a polygon roughly encompassing the approach or exit. Polygons are typically drawn with 3-5 vertices, although more can be used. Precision is not critical; the difference of a few pixels in any polgon vertex will not be significant in the software's output.

When the polygon has been completed (closed), it will appear green. If there are any errors (polygon not closed, or polgon contains elements intersecting itself), it will be colored blue (to represent non-closure) or red (to represent self-intersection) and it cannot be saved.

Example Paths

VTC provides an alternative method of configuring turn-movements for classification. Using the "Example Path" feature, users can draw individual paths for movement-counting. This allows users to specify more complex paths than would be possible with the region-based method. Example Paths are useful for roundabouts, highways with many lanes, and splits in the road.

In order to create an Example Path, click the '+ Path' button in the Region Configuration editor. Give the Approach and Exit a name (for example: Approach 1, Exit 1). Assign a turn-type to this movement using the drop-down selector (left/right/straight, etc). The "Ignored" check-box causes this turn to be classified, but discarded in counts. This is helpful when the user wants VTC to make a distinction between several movement types, but does not want to count all of them. The "Pedestrian-only" check-box causes this path to be used only for classifying pedestrian movements; typically this is used for representing cross-walk paths or pedestrian walk-ways where vehicles do not travel.

After configuring the Example Path approach and exit, click the newly-added Example Path button in order to draw the path. Click points in the desired path from start to finish using the background image, and select 'Done' when the path is complete. Paths should include at least 8 points. Hovering over the Example Path button with the mouse allows the user to confirm that the path has been placed correctly.