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SPEED — LAW ENFORCEMENT
DEVICES AND METHODS ARE USED TO ENFORCE SPEED LIMITS
Police officers must be able to accurately measure vehicle speeds. Methods vary, but most fall under the general types listed below. Radar: Radar is the primary method of speed enforcement in the United States. Radar guns aim an electromagnetic signal at a target vehicle and pick up the return signal reflected off the vehicle. The Doppler effect causes the frequency of the return signal to shift by an amount dependent on the relative speeds of the source of the original signal and the target. Speed radar devices measure the frequency of the reflected signal and compare it with the frequency of the original signal to determine the speed of the target vehicle. Radar is highly reliable and accurate. However, it can be difficult to pinpoint specific vehicles in heavy traffic, and some motorists use radar detectors to help them speed without getting caught. Laser: Laser devices, also known as LIDAR (light detection and ranging), use a time/distance calculation to measure speed. The devices aim a narrow band of light at the target vehicle and measure the time it takes to receive the reflected light. Because the speed of both the original light pulse and its reflection are traveling at the same speed (the speed of light), differences in the time it takes the transmitted light to strike the target vehicle and return can be used to calculate the speed of the vehicle. Lasers can pinpoint specific vehicles in heavy traffic. Devices to detect lasers have been marketed, but the narrowness of the laser beam reduces the likelihood that a laser detector can identify the beam in time to provide drivers with enough advance warning to slow down and avoid a ticket. VASCAR: VASCAR stands for visual average speed calculator and recorder. It uses a portable computer to accurately clock, calculate, and display speed based on the time a vehicle takes to travel a known length of road. VASCAR provides an average speed measurement over a greater distance than is possible with radar. It enables police officers to identify specific speeding vehicles and can be used from patrol cars following speeders. VASCAR can detect speeding vehicles going in the opposite direction. When used correctly it's very reliable. It emits no radiation, so it can't be picked up by radar detectors. Aerial speed measurement: Officers in light aircraft measure vehicle speeds based on the time it takes to travel between two or more pavement markings spaced a known distance apart. Information is transmitted to officers on the ground who then issue speeding citations. Speed cameras: Most speed cameras measure the speed of a vehicle at a single spot. One approach is to use a low powered Doppler radar speed sensor. Another is to use detectors embedded in the road surface. When a vehicle is driven over the detectors they trigger an electronic device that measures the vehicle's speed. In either case, if a vehicle is traveling faster than a predetermined speed, a motor driven camera goes off. The date, time, location, and speed are recorded along with a photo of the vehicle. More recent technology can measure average speeds over a certain distance. In this case, cameras located at two or more points record time stamped images of all vehicles that pass them. Automatic license plate recognition is used to match individual vehicles so that average speeds between the two points can be calculated. Time stamped pictures of speeding vehicles are used as evidence of speeding. Point-to-point speed cameras have been used to enforce speed limits in Australia and the United Kingdom.
Radar detectors are radio receivers tuned to the frequency range used by police radar guns. Radar detectors are bought and sold for the sole purpose of helping speeders avoid speeding tickets.
Institute research has shown that interstate highway drivers with radar detectors reduced their speeds by at least 5 mph or activated their brake lights when suddenly exposed to Radar detectors cannot pick up laser light. Speeders ticketed by police in Charleston, South Carolina, using laser devices were four times as likely to have radar detectors as motorists apprehended by officers using conventional radar. Clearly, the only purpose of a radar detector is to avoid speed law enforcement.
Research shows that drivers with radar detectors consistently are over represented among the fastest speeders. Use of a detector demonstrates an intention to speed that distinguishes users of these devices from drivers who speed occasionally or inadvertently. In a survey of users, more than half admitted to driving faster than they would without their "fuzz busters." Surveys of trucks in 24 states conducted before the federal government banned radar detectors in commercial vehicles involved in interstate commerce found that about half of all trucks on interstates had radar detectors in use.
Since January 1994, the US Department of Transportation has prohibited radar detector use in commercial vehicles involved in interstate commerce. Radar detectors also are banned in all vehicles in Virginia and the District of Columbia and in large trucks in New York and Illinois.
Institute researchers measured speeds and radar detector use in large trucks in 17 states in 1990 before the federal ban and found that more than half of all trucks, including half of trucks carrying hazardous materials, were using radar detectors. Use rates ranged from 39 percent in California to 69 percent in Oklahoma. An earlier study in Virginia and Maryland showed that trucks with radar detectors were more likely than those without them to be traveling at illegal speeds. On interstates with 65 mph speed limits, trucks using radar detectors were twice as likely as those not using detectors to travel at least 5 mph faster than the limit, and 3 times as likely to travel at least 10 mph faster. More than 3,000 people were killed in crashes involving large trucks in 2009, and most of them were not truck occupants. High speeds play a big role in truck crashes because they increase the already long distances required to stop a large truck. Speed also exacerbates the size and weight differences of trucks and passenger vehicles leading to more severe crashes.
States have a legitimate interest in banning the possession and use of radar detectors, and well written laws stand up in court. No court has held that the concept of radar detector bans, either by statute or regulation, is restricted by the Constitution. In fact, a US Court of Appeals in 1995 unanimously upheld the federal government's ban on radar detector use in commercial vehicles operating in interstate commerce.
Few other countries allow passenger vehicle drivers to use radar detectors. Among 21 nations surveyed by the Institute in 1994, the United States, Iceland, Japan, the Netherlands, New Zealand, Spain, and some Canadian provinces allowed radar detectors. In most other countries, it is illegal to sell or use radar detectors. Fines for violations can be as steep as thousands of dollars, and the prohibited devices may be confiscated.
Police can use radar detector-detectors to identify vehicles equipped with radar detectors. These electronic devices work by identifying the characteristic microwave radiation emitted by radar detectors.
The number of drivers and vehicle miles traveled have risen faster than the availability of officers whose routine duties include traffic law enforcement. In some jurisdictions, available traffic enforcement resources have declined as apprehension of violent criminals and homeland security efforts take priority. In addition, it may be difficult to observe speeds at the worst places and times. In congested areas, there may be no place to pull over violators without creating hazards. Automated speed enforcement can substantially reduce speeding on a wide range of roadway types. Institute studies in Maryland, Arizona and the District of Columbia found that the proportion of drivers exceeding speed limits by more than 10 mph declined by 70, 95, and 82 percent respectively after cameras were introduced. A 2010 review published by the Cochrane Collaboration, an international public health organization, examined 35 studies from various countries. The authors concluded that speed cameras, including fixed, mobile, overt and covert devices, cut average speeds by 1-15 percent and the percentage of speeding vehicles above the speed limits or designated speed thresholds by 14-65 percent compared with sites without cameras.
The effects of automated speed enforcement on crashes have been the subject of a considerable number of research efforts. A 2005 review analyzed data from 14 studies and found crash reductions in the immediate vicinities of camera sites ranging from 5 to 69 percent for all crashes, 12 to 65 percent for injury crashes, and 17 to 71 percent for fatal crashes. A 2007 review of 13 studies reported injury crash reductions of 20 to 25 percent for fixed speed cameras and 21 to 51 percent for mobile speed camera programs. In 2010, the Cochrane Collaboration reviewed 28 studies that reported the effect on crashes and found reductions of 8-49 percent for all crashes, 8-50 percent for injury crashes, and 11-44 percent for crashes involving fatalities and serious injuries, in the vicinity of camera sites. Over wider areas, the review found reductions of 9-35 percent for all crashes, and 17-58 percent for crashes involving fatalities and serious injuries. Reviewed studies with longer duration showed that these trends were either maintained or improved with time.
No. Speed cameras usually are programmed so they will not be activated unless a vehicle is traveling significantly faster than the posted limit — typically 10 or 11 mph faster, although in certain places such as school zones the grace levels may be lower. A visible police presence typically accompanies photo radar in the United States to maximize the deterrent effect. Portable units are placed at the roadside in or near a marked police car, and signs usually announce that photo radar is in use.
Speed cameras are used in 104 US communities in Arizona, Colorado, Illinois, Iowa, Louisiana, Maryland, Missouri, New Mexico, Ohio, Oregon, Tennessee, Washington, and District of Columbia. In Illinois and Maryland, cameras are used statewide in highway work zones. In Colorado, Maryland, Utah, and Washington, cameras are used statewide in school zones.
Yes. Telephone surveys conducted in 3 US jurisdictions with speed camera programs show a majority of drivers supported them. A survey conducted 9 months after speed cameras were introduced in the District of Columbia, showed that 51 percent of drivers favored cameras and 36 percent opposed them. Support for camera enforcement was higher among middle-age and older drivers, among drivers who had not received a speeding ticket in the mail and did not know anyone who had, and among drivers who said speeding was a problem. A survey conducted 6 months after speed cameras were deployed in Montgomery County, Maryland, found that 62 percent of drivers were in favor of speed cameras on residential streets. Support was higher among females and drivers 65 and older. In Scottsdale, Arizona, 63 percent of drivers surveyed prior to the start of automated enforcement said speed cameras should be used on an urban freeway where camera enforcement was planned. After speed cameras were operational, 77 percent of drivers supported their use.
Yes. Roadside electronic signs that display vehicle speeds to warn drivers they are speeding may reduce speeds and crashes at high risk locations. Institute research found that mobile roadside speedometers can reduce speeds at the sites of the speedometers as well as for short distances down the road. When used in conjunction with police enforcement, the effect of speedometers can last longer. Signs warning truck drivers that they are exceeding maximum safe speeds on exit ramps reduced the numbers of trucks traveling greatly above maximum safe speeds. Intelligent speed adaptation is an emerging technology that links the position of a traveling vehicle via GPS technology and computerized maps with speed limits to determine if the vehicle is speeding. The system may work as an advisory system for the driver or an intervention system that automatically reduces the vehicle's speed to comply with the speed limit. © 2013 TLC Magazine Online, Inc. |
