Distance Between Cars
The "Distance Between Cars" feature, or DBC, is an optional feature that can be integrated into the firmware capabilities of LTI's Marksman and Ultralyte laser guns. This special operating mode is used to help enforce laws against tailgating by measuring the time and distance between two moving vehicles.
Although DBC technology has been available since 1995, up until recently it has been mostly restricted to foreign markets. However, recently this feature has gained interest in the US, and it is reportedly being used or tested in a number of US jurisdictions, including some areas of Oregon, Colorado, Arizona, New Mexico, and Tennessee.
One NHTSA research report describes the basic process required for taking a DBC measurement:
"To achieve accurate measurement of the distance between two vehicles, the officer must first aim at the front of the first vehicle and press the trigger of the unit. Then the officer must quickly aim at the front of the second vehicle and press the trigger to receive the measure of distance, expressed in either feet or seconds. Because the reported distance is measured between the fronts of the vehicles, the officers must mentally estimate and subtract the length of the front vehicle from the reported distance in order to obtain the length of the gap between the two vehicles."
Reviews of the feature are somewhat mixed. The same report says that officers found the feature difficult to use:
"However, despite its obvious public relations value, officers found the DBC equipment to be an impractical way to measure tailgating. Officers found it difficult to accomplish the needed quick and accurate aiming of the laser in heavy traffic. In addition, the entire procedure was complex...In addition to the need for officers to develop skill in using the DBC equipment, its use required a team of two officers: one officer to operate the equipment and a second officer to apprehend the violator."
One news article reported that according to LTI, DBC has been challenged in court only once, in Arizona, and the technology was upheld.
Laser jammers that are effective against the LTI guns should also be effective against DBC.
More Information about Distance Between Cars: