Technology Transfer Series
Within the past few years the use of lidar speed measurement devices for speed limit enforcement by police agencies has steadily increased. LIDAR (LIght Detection and Ranging) is more commonly known as a laser speed measurement device. To insure the devices are accurate and reliable, there is a need for independent testing. To fill this need, the International Association of Chiefs of Police (IACP), requested that the National Highway Traffic Safety Administration (NHTSA) establish minimum performance specifications for lidar speed measurement devices.
How Lidar Works
Using a very narrow beam, lidar transmits infrared light pulses to a target. In speed monitoring tasks, this narrow beam allows a lidar operator to target a specific vehicle for speed measurement. The light pulses travel to the target and back again. Measurement of the elapsed time of the light beam to reach the vehicle and return computes the vehicle's distance from the operator. Changes in the distance provide the vehicle's speed. The device is often called a laser speed gun because the source of the lidar light is a laser.
Lidar Minimum Performance Specifications
At NHTSA's request, the National Institute of Standards and Technology (NIST), US Department of Commerce, developed model performance specifications and testing protocols for laser speed measurement devices. Several years ago, NIST also developed model performance specifications for police traffic radar. The results of the current lidar project, Model Minimum Performance Specifications for Lidar Speed Measurement Devices are now available. Completed in December 1994, these model specifications are being widely distributed to law enforcement agencies and highway safety officials. They are also available to the public.
The U.S. Department of Health and Human Services, Food and Drug Administration's Center for Devices and Radiological Health (CDRH), has rated the lidar speed units currently on the market as Class I devices. Class I is the lowest classification of a laser product in terms of relative potential risk. NHTSA recommends that law enforcement agencies use only lidar speed instruments that have been rated Class I by CDRH.
The IACP, with NHTSA support and funding assistance, is establishing lidar testing laboratories at two universities. Both of these laboratories are currently testing police traffic radar and are being equipped to test lidar.
The International Association of Chiefs of Police will manage testing of lidar units to determine if they meet the minimum performance specifications. Devices that meet the specifications will be placed on the IACP's Consumer Products List for Radar and other speed measurement devices. This list, which is published and periodically updated by the IACP, provides law enforcement agencies and highway safety officials with the name of each Radar and lidar device that meet the minimum performance specifications.
In 1995, NHTSA will publish and distribute a model basic operator training course in lidar speed measurement. In modular form, the course includes 24 hours of formal classroom instruction. After successfully completing a written exam, a trainee must also successfully complete 16 hours of supervised field practice, leading to certification. Course topics are:
NHTSA believes that lidar speed measurement is an effective tool for speed limit enforcement. Lidar provides an additional means for increasing the effectiveness of speed enforcement programs and enables police managers and other highway safety officials to better deter speed related crashes. Purchasing lidar units based upon their perfor-mance capabilities will help get the best equipment in the hands of law enforcement officers.
Together, the testing process and training program will help assure law enforcement agencies, the public and the courts, that lidar is a safe, reliable, and accurate way to measure vehicle speed. These specifications were developed in accordance with the joint NHTSA and FHWA Speed Management Work Plan issued January 1995.
For a copy of Model Minimum Performance Specifications for Lidar Speed Measurement Devices or for more information about this program, contact Bernard J. Moran, Police Traffic Services Division, NHTSA, NTS-41, 400 Seventh Street, S.W., Washington, DC 20590, (202) 366-4292, or send a fax to (202) 366-7721.
400 Seventh Street, S.W. NTS-33
Washington, DC 20590
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