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Traffic Lights Violation

Definitions

A “Traffic light violation” occurs if a car:

  • Enters a crossroads by crossing the entry line (e.g., the “In” line below) after the red light gets switched on,

AND

  • Leaves the crossroads by crossing the exit line (e.g., the “Out” line below) before the red light goes off.
Diagram of a crossroads with dashed Entry (In) and Exit (Out) lines and a red traffic light icon
Timeline labeled Case A showing the entry and exit lines both crossed while the traffic light is red

The platform records a violation only if the “Do not go” light selected in the violation rule was on when the vehicle crossed the entry line and shortly before that.

However, a minor mismatch between entry/exit timestamps vs red light goes on/off is considered permissible. It must be less than Ignore signal for … sec parameter value. This is to avoid too many minor violation events.

Diagram of the Ignore signal for … sec tolerance window around the red light on and off transitions relative to when a car enters or exits the crossroads

If the stop line control is also enabled at the crossroads, traffic light violations can occur in situations like this:

Timeline labeled Case B showing the entry line crossed while the light is red and the exit line crossed after it turns green, within the Time to cross limit

Note icon The timestamp of the event when the car crosses the line is detected, considering the value of the Focal point.

Note icon The entry-to-exit time span should not exceed 180 seconds; otherwise, it is not considered a violation.

Note icon A crossroads may be complicated enough to have multiple entry and exit lines. A car, in its turn, may make a tricky maneuver at the crossroads, crossing many of them. To avoid confusion in a situation like this, the program automatically builds forbidden entry-exit pairs in a way illustrated by the diagram below. i.e. a pair is built from the lines crossed strictly in turn, with account of the entry-to-exit direction.

Timeline diagram showing entry and exit lines crossed in turn, illustrating how the system pairs each entry line with the next exit line crossed

Note icon  An arrow in an "Off" condition shall not be considered a "Do not go" signal if the yellow circular light is continuously flashing, thus signalling that the crossroads is out of control.

Traffic light with a continuously flashing yellow circular light above an arrow signal, indicating the crossroads is out of control

Workflow to Set Up Traffic Lights Violations

  1. Build a road object.
  2. Bind cameras to the road object.
  3. Name the violation
  4. Build the entry and exit lines
  5. Set up the “Do not go” signal.
  6. Combine the lines and signal into a rule.
  7. Turn on traffic lights control.
  8. Review the result.

Build the Entry and Exit Lanes

In the CarTrack Pro settings for the camera monitoring entry or exit to and from the road object, build the entry and exit lanes. Give these lanes clear names, e.g. “In” or “Out,” to make it easier to combine them with the “Do not go” signal into a rule later.

Set Up Traffic Lights Control

On the camera designated to monitor the traffic lights, set up the circular lights and arrows that control traffic across the road object. Give the monitored lights and arrows self-explanatory names, e.g., “Left-pointing arrow.”

Formulate the Rule

Now combine the lanes and traffic lights into the rule.

  1. On the road object page, open the Options menu and select Violation rules.
  2.  Under Cameras click the camera label meant to monitor the entry to the road object (arrow 1 in the picture below).
  3. Under Traffic objects click the entry lane (e.g. "In", see arrow 2), which is one of the Entry lanes build here.

    Violation rules panel with the Entry and exit camera label selected and the In traffic lane chosen under The 5th and Broadway road object

  1. Click "+" to select the planned traffic light violation name (e.g. "Left turn under red") under Traffic lights violations.

    2. Violation name list with Left turn under red selected under Traffic lights violation

  2. On the next screen in the Traffic lights text  box select the label of the camera watching the traffic lights, e.g., "Arrow control".

    3. Left turn under red rule with Arrow control selected as the Traffic lights camera and Left-pointing arrow - Light off selected as the Do not go light

  3. Under “Do not go” light find the name of the signal that controls traffic across the crossroads, e.g., "Left-pointing arrow". The platform records a violation only if that “Do not go” light was on when the vehicle crossed the entry line and shortly before that.
  4. Under that name, click the condition of the light that consitutes a violation when dring from the entry lane (e.g. "In") to the exit one. For instance it is "Light off" for an arrow.
  5. Define numerically the Time to cross, sec and Ignore signal for … sec parameters.

    6. Left turn under red rule with Ignore signal for … sec set to 3 and Time to cross, sec set to 20

  6. In the Exit lane box find the label of the exit camera, e.g. "Lane control".
  7. Under that name click the exit lane name, e.g. "Out".
  8. Click Save.

Turn On Control

Control on a road object stays off until it is turned on. On the road object page, open the Options menu and select Turn on control. In the Turn on Road Object control window, select Traffic lights violation and click Turn on.

With control on, the platform captures each violation and lists it on Find Traffic Rule Violations.