A small period of time, referred to as a grace period, and a preset speed necessary to activate the system are usually allowed in order to differentiate between vehicles attempting to stop or turn right on red and vehicles that clearly are running the red light. A common grace period is 3/10 of a second (though an international standard of 0.5 seconds exists) and a minimum speed necessary to activate the system ranges from 15 to 20 miles per hour.

When the system is activated by a vehicle running a red light, at least two pictures are taken by the camera. The first picture shows that the front of the vehicle is not in the intersection when the traffic signal is red. This picture must show the pavement marking defining the intersection (usually the stop bar or the crosswalk), the traffic signal displaying a red light, and the vehicle in question .

The second picture then shows the vehicle in the intersection a short time later (0.5 to 1.5 seconds). If driver identification is necessary, a third picture of the driver may be taken. From the pictures taken, the license plate will be magnified to allow for identification.