Lidar traffic enforcement
Speed estimation takes less than half a second, which, together with the narrow, targeted beam, results in offending vehicles having little warning even when using an evasion device.
This occlusion issue does not apply to fixed speed enforcement devices that can be mounted on poles or gantries up to 5-6 meters / 15 -20 ft high using radar as detection method.
[2] The light emitted is required to be in the infrared range, meet eye safety standards, and have pulse repetition less than one kHz with beam divergence less than 5 milliradians.
Vehicle registration plates are an important part of traffic enforcement and in most jurisdictions the government holds a monopoly on their manufacture, although this may be contracted out.
Normally it is illegal for private citizens to modify, make and affix their own plates, as this is equivalent to forging an official document.
California plates are required to be 6 in tall and 12 in wide, a usual standard, and have a reflective surface that is particularly sensitive to infrared light,[9] which enables it to be imaged at night, enables Automatic License Plate Recognition, allows LIDAR devices to receive a strong reflective signal return, and have tamper-resistant markings.
Police generally prefer to detect from the front while observing oncoming traffic, which also enables the offender to be waved over and avoid the risks of high speeds required to catch up to the vehicle.
A number of jurisdictions prohibit any methods to thwart speed limit enforcement, and lidar manufacturers endeavour to stay ahead of detection avoidance measures.
Returning a false separate signal will be detected by current police lidar models and may not be legal, depending on the jurisdiction.
A typical NHTSA approved[7] lidar device emits 30 ns pulses of laser light with wavelength 905 nm and 50 milliwatts of power with 3 milliradian beam divergence.
An expert operator will use the viewing capability to select a likely offender prior to speed detection, this has the advantage that minimum signal is scattered to warn following vehicles equipped with lidar signal detection devices, this is not so important on sparsely trafficked roads and a lower capability lidar device may be used.
Normal weather conditions have negligible impact on device performance but may impede operator ability to target a vehicle.
In addition to expert testimony, the court noted that it factored scientific publications into its decision: The Court conducted an extensive four-day Frye [Daubert] hearing... [in which it] considered such issues as the basic science of laser technology, the technical methodology of, and theoretical challenges to, the reliability of radar guns... including the possibility of other “pulses” in the vicinity of use, difficulties in target identification, possible errors caused by vehicle license plates, windshield glass, shape, and color, and potential malfunction of the device.
A motorist may therefore not have sufficient time to respond to the burst transmission of a lidar device, or the narrow beam might be focused on a specific part of a vehicle where the sensor cannot detect it.
However, several states have passed laws that specifically prohibit the use of laser jammers, including: California, Colorado, Illinois, Iowa, Minnesota, South Carolina, Tennessee, Texas, Utah, and Virginia.
