Safety cameras are an important element in the Safer Essex Roads Partnership (SERP) road safety strategy.
There are more than 100 fixed speed camera sites and 26 red-light camera sites across the SERP’s area. The strategy also incorporates the use of mobile handheld devices, which allows for dynamic enforcement across the SERP’s area at locations where a fixed site would not be justified.
All enforcement cameras are highly technical pieces of equipment, and to explain how they operate in detail would require a highly technical description. However, in this section we explain in very simple terms how each camera type works.
All cameras used for enforcement purposes are Home Office Type Approved, which guarantees the integrity of the equipment and ensures the monitored results are accurate, when the cameras are used in line with the manufacturer’s instructions.
Many challenges to their accuracy have been raised over the years, but the level of testing required under the Home Office Type Approval process, and the practice of having all cameras annually calibrated, ensure their accuracy is maintained. Cameras are never used without a valid annual calibration certificate.
Camera types used in the SERP’s area
Fixed Site Speed Cameras
These are the single stand-alone units that are painted yellow and located by the side of a road. They are used in areas where there have been a number of fatal or serious collisions over a set period, and evidence that a high proporton of vehicles were exceeding the speed limit. The majority of cameras in the SERP’s area were introduced as part of the Department for Transport’s Safety Camera Programme which took place between 2000 and 2007.
Average Speed Cameras
While fixed site cameras encourage drivers and riders to maintain a safe legal speed, they only monitor one location. Average speed cameras, however, are able to cover a complete stretch of road by having a starting and finishing camera located at variable distances apart. Average speed cameras encourage drivers and riders to maintain a safe speed over a stretch of road, rather than at one location. As with fixed site speed cameras, average speed cameras are placed on roads where there has been a history of fatal and serious collisions.
Managed Motorway Cameras
Managed Motorway Cameras have been recently introduced on the M25 in Essex. They are a fixed camera, generally located on the side of a motorway gantry, fitted with variable electronic speed limit signs.
They vary from the usual fixed cameras in two key areas: first, they are not painted yellow (it should be noted there is no legal requirement for any camera to be painted); and they are able to automatically pick up the speed limit displayed on the variable gantry signs, and monitor vehicle speeds that exceed the speed limit being displayed at the time.
Mobile Hand-held Cameras
SERP uses a ‘Trucam’ device which, although hand held, is able to store video evidence of a vehicle, and records all the required speed data of the vehicle being monitored.
Fixed Red Light Cameras used in the Safer Essex Roads Partnership (SERP) area
Fixed red-light enforcement cameras
These camera installations are single stand-alone units that are located on one or more approaches at a traffic signal controlled junction; there are currently 26 installations in the SERP’s area.
The camera housings are painted yellow for added conspicuity and have been installed at locations where there has been a history of personal injury collisions involving at least 1 driver or rider that has disobeyed a red traffic signal.
In advance of all red-light camera installations there are advisory signs warning road users of the presence of the red-light camera. The majority of red-light enforcement cameras in the SERP’s area were installed during the Department for Transport’s Safety Camera Programme that took place between 2000 and 2007.
How do red-light cameras work?
The red-light enforcement cameras currently used in the SERP’s area use inductive loops buried in the carriageway in the vicinity of the stop-line to detect vehicles that disobey a red traffic signal. The cameras are triggered when a vehicle crosses the stop line at the same time a red signal is showing. When an offending vehicle is captured, two photographs are taken less than a second apart to show the vehicle travelling across the junction when the red signal is displayed. The speed of the offending vehicle and the time the red signal had been displayed when the offence occurred is also recorded.
How do cameras work?
Safety cameras operate in different ways – here is a simple guide as to how they work.
Fixed Site Speed Cameras
Fixed site speed cameras used in the SERP’s area utilise a ‘passive radar system’; a radar signal is constantly sent out from the camera site and if no vehicle is in its range the signal does not bounce back. If a vehicle goes by, the radar signal is bounced back to the camera, and when this happens the camera is able to calculate the speed of the vehicle.
When a signal is bounced back above a pre-set minimum speed, which is above the speed limit of the road, the camera takes two photographs 0.5 seconds apart.
These two photographs capture information to enable a ‘secondary check’ to take place. The vehicle goes past the camera site, after which there are a number of white lines painted in the road, at a known fixed distance apart. Comparing the two photographs, taken 0.5 seconds apart, allows the distance the vehicle has travelled in that time to be seen. The known distance covered in 0.5 seconds allows the simple calculation of distance over time to give the speed, which provides the secondary evidence that the vehicle was committing an offence.
Average Speed Cameras
Average speed cameras use the simple science of physics; that a vehicle covering a set distance, in a set time, will give you an average speed over that distance. A camera is located at the beginning of a stretch of the road being enforced, with a second camera located at the end of the stretch.
The cameras use a combination of infra-red and normal digital photography. The first infrared cameras record the number plates of all of the vehicles entering the enforcement area, which the second infrared camera at the end of the enforcement area records the number plates of all vehicles as they exit the stretch of road being enforced.
The system checks all vehicles and the time it has taken for them to drive the fixed distance between the cameras.
If the average speed is above the threshold set – and only if the threshold is exceeded – the third normal digital camera takes a photograph of the vehicle in question.
The hand-held cameras used by SERP use a laser to check the speed of a vehicle. When an operator sees a vehicle approaching, they first assess whether, in their view, the vehicle appears to be travelling above the set speed limit. If they believe this to be the case, they aim the hand held camera on the vehicle, and when the vehicle is aligned in the target area shown on the camera screen, the operator presses the trigger.
A series of beams are fired at the vehicle which reflect back to the camera, and the time difference between the beams being sent out and returned gives the vehicle speed.
The hand-held cameras used by SERP also record a continuous video image which provides evidence of the offending vehicle.
Other hand-held cameras used by the police operate in a similar way but are not capable of storing a moving image of an offence. In these cases the officer will physically stop the vehicle, take the driver or rider’s details and issue a ticket.
Managed Motorway Cameras
These operate in a similar way to fixed site cameras as they are radar-based operation. The two key differences are: first, no secondary check lines are required on the road itself as the camera uses screen based lines to show the distance travelled in a set time; and second, unlike fixed sites the managed motorway system is a variable speed.