Gatso is the brand that Gatsometer BV (now known as Sensys Gatso Group, after being acquired by Sensys in 2015) use on their speed cameras and red light cameras.

The most commonly encountered Gatso speed cameras emit radar beams to measure the speed of a passing vehicle. If the vehicle is travelling above the preset trigger speed, one or two photographs are taken (depending on the device's setting, which generally depends on the requirements of the local jurisdiction). These use a powerful flash, to show the rear of the vehicle, its registration plate, and calibration lines on the road (in many jurisdictions).

Newer installations used digital cameras which have limited exposure latitude compared to film. These installations use an auxiliary flash placed close to the position where a speeding vehicle would exit the radar beam and the first photograph would be taken.

Gatso installations in the United Kingdom and in Queensland, Australia, are characterised by a measurement strip on the road surface, which is a series of white lines painted on the road, which are used with two photographs taken by the camera. These white lines are sometimes known as 'secondary check marks'. The camera is set to take two photographs, with a constant time interval between them, usually 0.5 seconds for faster roads and 0.7 seconds for slower roads. The difference in the vehicle's position in the two photographs can be used to calculate its speed.

In the UK, the evidence is admissible in court using the speed measured by the radar. The speed calculated from the distance travelled between the photographs using the secondary check mark white lines is used by police forces to verify the radar reading, and can be used as a defence in the event of an unreliable reading by the radar.

It can be a common misconception by drivers that the police do not use the distance travelled between the secondary check marks before issuing a notice in the post. The police can make mistakes, but the combination of radar reading and secondary check marks is a robust case for prosecution.

The speed indicated by the radar unit can be prone to error due to multiple reflections etc. With a minority of vehicle types such as lorries towing a curtain sided trailer. Further, it does not distinguish between multiple vehicles in shot, however secondary check marks will identify which vehicles are speeding, providing the police with corroborative evidence.

The first red light cameras were introduced in an initiative in the City of Nottingham in 1988 following a triple fatal road traffic accident at a traffic light controlled road junction.^{[citation needed]}