This thread was started with a technical question. It deteriorated into something less than technical in nature. Everyone has an opinion. Nobody wants to hear anyone else's opinion unless it is congruent with his or her own. Enough said.
If anyone cares to know, this is how speed limits are set in California: An unmarked car will sit at the desired location where the "traffic engineering survey" is to be taken. The person in the car utilizes a radar gun to record the speed of all vehicular traffic. The speed limit is then calculated as the 80th percentile of the speed of all the traffic recorded during the survey. Therefore 20 percent of future traffic will be in violation of the newly established speed limit, regardless of the drivers prudence (or lack thereof). This type of traffic engineering survey is performed wherever a clear speed limit cannot be ascertained via roadway engineering considerations, or where prevailing state law is clearly applicable.
Regarding the laser radiation -- not only is the intensity very low (I forgot how many milliwatts), but it is also in the infrared spectrum (904 nanometers to be precise). The human eye does not register this wavelength. The method of jamming a laser signal is to feed enough infrared light back to the laser gun to overwhelm its own reflected signal, thereby confusing the gun. This is how the commercial units work (or don't work, depending upon the source of information).
It is definitely illegal to jam a radar signal, as it requires the use of radar transmitting equipment and therefore the operator and the equipment must be licensed by the FCC. The commercially available laser jammers are kind of in a gray area here. While it is technically not illegal to transmit infrared light, it can still be construed as interfering with the official duties of the officer operating the equipment -- such interference is definitely frowned upon, and theoretically could land you in jail.
The Automobile Association of America (AAA) has for many years now ‘donated’ speed-measuring equipment (meaning radar guns) to innumerable police agencies throughout the U.S. It may be hard to believe but at one time the AAA used to organize racing events, predating the SCCA. Now that they are in the auto insurance business, they have discovered that is fiscally prudent to enhance the revenue generating capabilities of police agencies. Remember that when you receive a ticket, it is not just the traffic fine that is being paid -- insurance companies see a fringe benefit from additional ‘points’ to on your license.
If anyone knows of a source where 904 nanometer LEDs can be purchased, please let me know. I am quite serious -- I researched this sometime ago but could not find a source for the LEDs. It should be fairly simple matter to construct a do-it-yourself project. This of course would be used for experimental purposes only.