A red light camera (short for red light running camera) is a type of traffic enforcement camera that captures image of vehicle that has entered an intersection in spite of the traffic signal indicating red.
A red light camera (short for red light running camera) is a type of traffic enforcement camera that captures image of vehicle that has entered an intersection in spite of the traffic signal indicating red.
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Red-Light Cameras How do red-light cameras work?

Author / Editor: Luke James / Erika Granath

We are sure you are no stranger to red lights and the fact that many of them have cameras, but have you ever thought about how they work and the purpose they serve?

Red-light cameras (or “red-light running cameras”) are used to try and prevent drivers from running red lights. Although they are most commonly seen at some of the most collision-prone intersections and junctions on roads around much of Europe and America, they can be found anywhere—there are no “rules” that stipulate where they can and cannot be deployed.

Although the specific features of red light cameras can and do vary by location, particularly between countries, the way they work and their effectiveness is pretty standardized worldwide.

Also, studies have indicated that the use of red light cameras, where adequate warnings are displayed, actually reduces accidents. This is because drivers are more likely to exercise caution when approaching an intersection or junction where they know a camera is present, reducing the likelihood of a driver running a red light and potentially causing an accident.

How red light cameras work

Whilst red light systems rely on sophisticated technology, they are conceptually simple. Most systems consist of only three elements: camera(s), sensor trigger(s), and a computer. There are many different trigger technologies, but they all serve the same purpose: They detect when a car has moved past a point in the road when it shouldn’t have.

The most common trigger technology is the induction loop. This type of trigger is a length of electrical wire buried just beneath the road surface. It is typically laid out in rectangular loops resting on top of each other. This wire is hooked up to a power source and a meter. This meter continuously monitors the circuit’s inductance level, and when a car passes over the wire, this causes a significant change in inductance and causes the computer to recognize that a car has passed over it.

What happens when a red light camera is triggered?

Red-light cameras take photographs of vehicles that enter the bounds of a specific intersection, mapped by the induction loop after the traffic light has turned red. Generally, red-light cameras are either mounted directly to the traffic light stand or on a free-standing pole near to the intersection or junction.

When the light turns red, any vehicle going where it shouldn’t trigger the camera. When the camera is triggered, a picture is taken of the vehicle and its license plate. Sometimes, they can even snap a picture of the driver, however, the picture usually only captures the license plate, and therefore, the registered owner is more often than not the person on the hook for the offense.

Penalties for running a red light

Once a camera has taken a photo, a ticket is automatically generated and sent to the registered keeper of the vehicle. Alternatively, a police officer (or other trained officials, such as a local authority) may review the picture who decides whether the driver was, in fact, running a red light.

Depending on local laws, punishments can range from anything to a minor ticket all the way to license “de-merit” points or similar; whether the impact is solely on the registered keeper’s bank account or their driving record is dependant entirely upon local laws.

In the UK, for example, the minimum penalty for running a red light is a fine of £100. There is also the chance of being awarded three license points. Accumulate 12 of these (or six within your first two years as a new driver), and you lose your license. Points last for three years before being wiped from your driving record.