Road-rule enforcement camera

From Academic Kids

A red-light camera in use in
A red-light camera in use in Beaverton, Oregon

A road-rule enforcement camera is a system including a camera and a vehicle-monitoring device used to detect and identify vehicles disobeying a road rule or road rules. Common examples include the following:

  • Speed cameras for identifying vehicles travelling over the legal speed limit.
  • Red-light cameras for identifying vehicles proceeding through red lights.
  • Bus lane cameras for identifying vehicles traveling in lanes reserved for buses and/or vehicles engaged in car pooling.
  • Toll-booth cameras for identifying vehicles proceeding through a toll booth without the toll being paid.
  • Level crossing cameras for identifying vehicles crossing railways at grade illegally.
  • In central London, cameras help to identify drivers who evade paying the Congestion Charge.

There are systems that are combinations of the above - for example, some systems detect both red-light infringements and speed infringements.



A Dutch company called Gatsometer BV, founded by the 1950s rally driver Maurice Gatsonides, invented the red-light camera, developed the first radar for use with road traffic, and is the world's largest supplier of speed camera systems. Because of this, in some countries speed cameras are sometimes referred to as "Gatsos". They are also sometimes referred to as "photo radar", even though many of them do not use radar.

The first systems introduced in the late 1960s used film cameras to take their pictures. From the late 1990s, digital cameras began to be introduced. Digital cameras can be fitted with a modem or other electronic interface to transfer images to a central processing location automatically, so they have advantages over film cameras in speed of issuing fines, and operational monitoring. However, film-based systems still generally provide superior image quality in the variety of lighting conditions encountered on roads, and in some juristictions are required by the courts due to the ease with which digital images may be modified. New film based systems are still being sold.


Vehicle-detection systems used in conjunction with road-rule enforcement cameras include the following:

  • Piezo-electric strips - pressure-sensitive strips embedded in the roadway (a set distance apart if speed is to be measured - typically 1-3 meters).
  • Doppler radar - a radio signal is directed at the vehicles and the change in frequency of the returned signal indicates the presence of a moving vehicle and the vehicle's speed.
  • Loops - inductive loops embedded in the roadway detect the presence of vehicles, and with two loops a set distance apart vehicle speed can be measured.
  • Laser - the time of flight of laser pulses is used to make a series of measurements of vehicle position, and from the series of measurements vehicle speed can be calculated.
  • Automatic number plate recognition (ANPR) systems that use a form of optical character recognition to identify the license plate

Systems can be car or van mounted, hand held, or in a fixed site. In car-mounted systems, cameras and radars or lasers are fixed to a car. When deployed, the car is parked beside a road, and any speeding vehicles driving past are photographed. Most red-light cameras, and many speed cameras, are fixed-site systems, mounted in boxes on poles beside the road. They are also often attached to existing gantries that hold up signs over the road, or to overpasses or bridges.

Speed camera systems that measure the time taken by a vehicle to travel between two fairly distant sites (from several hundred meters to several hundred kilometers apart) are also being developed and introduced. From the elapsed time over the known distance, a speed infringement can be detected, or in the case of truck drivers driving long distances, avoidance of legally prescribed driver rest periods can be detected. Such systems take a picture of every vehicle passing the first site, and every vehicle passing the second, then find matches between the images from the two sites. Most commonly, this matching is done by using ANPR systems.

Verification and system testing

In the UK, every speed camera must be calibrated and certified before the images from it are acceptable to the court, including the cameras used in police vehicles. Several speeding prosecutions have failed in the UK due to out of date calibration certificates.

The pictures taken by road-rule enforcement cameras must usually be viewed by a person before any infringement notice or ticket is issued to the driver, and judged to be satisfactory or not. This step is known as verification, and is a standard legal requirement in nearly all jurisdictions. Verifiers typically must check some or all of the following:

  • that there is no sign of interference with the vehicle detector by objects other than the alleged speeding vehicle,
  • that the license plate is unambiguously readable according to a legal standard,
  • that the make and model of vehicle matches that recorded by the licensing authority for the number plate,

and in some jurisdictions

  • that the appearance of the driver in the images is adequate in some way - for example, that it matches the picture on the driver's license of the vehicle's registered owner.

In most jurisdictions, verification is carried out by the police force, although in many places it is carried out by private companies on a fixed-price basis under close police supervision. Generally, cameras must undergo approval testing and operational testing to ensure that they function adequately. In the US, it is common for all installation, operation, and verification procedures to be carried out by private companies that receive payment based on the number of infringements they issue, and often under no testing regime whatsoever.

Depending on the number of things that need to be identified in the images and the quality of the camera equipment, somewhere between 35% and 80% of infringements result in a notice being issued to the owner of the vehicle. A legal requirement for driver identification reduces the prosecuting rate dramatically.


In September 2001, pictures from the San Diego red light camera systems were ruled inadmissible as court evidence (USA Today article (, Judge's ruling ( The camera program was operated and paid for according to practices common throughout the US. Such practices give a financial incentive for companies to verify against drivers in cases of doubt, and this was found to be unacceptable, as was the low level of involvement by the city and police. Despite the ruling, such verification and camera operation practices continued on a widespread basis in the US. Some states like California allow only red-light enforcement cameras but not photo radar speed enforcement cameras, as the latter type are seen as too intrusive.

In January 2002, a speed camera case was dismissed in Denver, Colorado on similar grounds of pay per infringements being illegal, and lack of police involvement in issuing of tickets.

In the late 1990s in a number of jurisdictions, there was a degree of controversy surrounding the deployment of increasing numbers of speed and red-light cameras. Police and government were accused of "Big Brother tactics" in over-monitoring of public roads, and of "revenue raising" in applying cameras in ways to increase government revenue rather than improve road safety. In some places, for example the province of Ontario, Canada, and the state of Hawaii, USA, camera programs were aborted or withdrawn due to public outcry. Often when camera deployment has been accompanied by large scale advertising campaigns explaining the justification and planned effects of such cameras, the public has accepted their use on a large scale. In other places, public responses have included spectacular vandalism of camera systems including attacks with explosives, tractors, cutting equipment, incendiary devices, rifles, and even attacks on camera operators, as forms of civil disobedience and protest.

In the United Kingdom, speed cameras are an increasingly political issue. The government and road safety campaigners claim that they are very helpful in accident 'hotspots', saving 1,000 people from death or serious injury each year; a government audit showed that 95% helped to reduce accidents[1] ( However, some motorists believe that many cameras are erected simply to make money for local councils or police (in the UK, the revenue from cameras can only be used to cover the costs of the cameras and their operation [2] ( In 2004, the Conservative Party accused the government of "waging a war on drivers" and announced that, if it came to power, it would review the effectiveness of all cameras in England and Wales, scrapping those which were ineffective.

In "driver responsibility" jurisdictions (example: California) the police need to have a photo of the driver's face, of sufficient quality to convince the judge that he is convicting the actual driver, not someone else who had access to the vehicle. Because many of the "face photos" are of very poor quality, the police have developed a novel way of improving the evidence. As of 2005 at least nine cities are known to mail some motorists a form letter [3] ( entitled "Traffic Violation Notice." These Notices have not been filed with the court and therefore response is not mandatory. They can be easily recognized as they do not have the court's address on them, and also carry the admonition, "Do not contact the court." The Notices say that you must respond within 10 days and that you must give the police the name and address of the driver pictured on the Notice, even if it is yourself.

Whether road-rule enforcement cameras save or cost lives is frequently debated. Opponents of cameras claim that improperly used speed cameras may cause drivers to brake sharply and accelerate again after the camera zone and that this risky driving behaviour could lead to more accidents and also that speed cameras distract police effort from other, more important, police tasks. Research from the UK Department for Transport [4] ( claims that at sites with speed cameras, the number of road users killed or seriously injured at camera sites fell by 40% after the installation of the cameras. Opponents of cameras make the counter argument that this effect can be explained by the fact that camera sites were chosen because they had a high number of accidents in the first place. The same report also claims that, taken as a whole, counties which introduced large numbers of speed cameras show a statistically significant reductions in deaths and injuries from road traffic compared to those which did not.

Various studies (, have linked red light cameras to an increase in the number of rear-end collisions where they are used. The theory is that a driver who stops suddenly in order to avoid getting a ticket may be hit from behind by a vehicle whose driver did not expect the sudden braking. A report commissioned by the Virginia Department of Transportation in late 2004 showed that the rear-end collisions contributed to an overall increase in injury accidents between 7 and 24 percent at camera-enforced intersections. As a result, the Virginia legislature declined to reauthorize its camera enforcement law and all red light cameras in the state will be removed as of July 1, 2005.

Counter technology

Methods used to avoid detection by cameras include

  • Simply braking before the camera
  • Anti-detector units that can detect the radar or laser emissions from hand held guns and static GATSO cameras, and flash a warning to the driver that they are being scanned. The UK police tried to make these detectors illegal in a test case under the Post Office Act, on the basis the guns caused radio interference with a legitimate radio transmission, but the case was thrown out, making the detectors legal in the UK
  • However, a different type of anti-detector, also available, will throw back laser or microwave signals to confuse the transmitting gun. These are illegal in the UK. There is the point that whereas a radar gun takes a short time to detect your speed, if the anti-detector warns you of a laser scan, it is too late because it has already logged your speed.
  • Yet another type of anti-detector uses the Global Positioning System to compare the vehicle's position against a database of known camera locations, warning the driver when one approaches. These databases have historically been compiled from contributions from members of the public, but this process has been greatly helped by some Safety Camera Partnerships now officially publishing camera locations. This solution has the advantage of being immune to other sources of electromagnetic radiation that can accidentally trigger detection-based systems. However, it has the disadvantage that the database must be regularly updated to reflect changes in camera deployment, which causes particular problems in the case of mobile cameras. It is possible to install such databases on some satellite navigation systems, effectively turning them into this type of device. More sophisticated models are able to warn the driver if the vehicle's speed is in excess of the speed limit when approaching a camera. There is no evidence that this type of antidetector is illegal in the UK.
  • The digital technology that reads your number plate could only be defeated if your number plate is unreadable. It is illegal in the UK to drive with unreadable plates, despite several companies claiming to sell stick on film that makes the numbers unreadable to the cameras. There is no evidence that these obscuring films work. In theory you could swap number plates between cameras, but the risks probably outweigh the benefits.
  • GATSO cameras can be defeated by placing a camera flash gun in the rear window of the car (or front windscreen), connected to a photosensitive cell. When the speed camera fires the internal flashgun to take the photograph, the flashgun in the car is also triggered by the photocell, over exposing the photograph. This is illegal in the UK.

External links

Example images

  • UK pics (

Against enforcement cameras

For enforcement cameras



Academic Kids Menu

  • Art and Cultures
    • Art (
    • Architecture (
    • Cultures (
    • Music (
    • Musical Instruments (
  • Biographies (
  • Clipart (
  • Geography (
    • Countries of the World (
    • Maps (
    • Flags (
    • Continents (
  • History (
    • Ancient Civilizations (
    • Industrial Revolution (
    • Middle Ages (
    • Prehistory (
    • Renaissance (
    • Timelines (
    • United States (
    • Wars (
    • World History (
  • Human Body (
  • Mathematics (
  • Reference (
  • Science (
    • Animals (
    • Aviation (
    • Dinosaurs (
    • Earth (
    • Inventions (
    • Physical Science (
    • Plants (
    • Scientists (
  • Social Studies (
    • Anthropology (
    • Economics (
    • Government (
    • Religion (
    • Holidays (
  • Space and Astronomy
    • Solar System (
    • Planets (
  • Sports (
  • Timelines (
  • Weather (
  • US States (


  • Home Page (
  • Contact Us (

  • Clip Art (
Personal tools