There are som 200,000 radar guns in operation in North America. A recent speed enforcement tool is the use of infrared laser guns operating at a 904 nanometer wavelength. Over 30,000 laser guns are presently being used by law enforcement. In Ohio, a laser gun is standard equipment in all 435 state police vehicles.

Laser has distinct advantages over traditional radar guns. At five hundred feet the laser's elliptical beam is a mere 18" wide compared to X band radar at one hundred and fifty-five feet. Laser works in a monochromatic format with a narrow spectrum by emitting infrared via a gallium arsenide diode at extremely high power. Infrared light is sent by the laser gun in a series of predetermined pulses, in excess of 300 per second, at the speed of light, 186,000 miles per second. Each emitted pulse is timed when it leaves the laser gun and when it returns. The difference form the time it leaves and returns is then computed in miles per hour. All this takes place in less than one third of a second.

Laser looks för flat, reflective surfaces of the target vehicle such as the front license plate. In the eighteen states and five Canadian provinces with no front plate, the laser is aimed at the headlights. Vehicular shape and color affect the laser gun's ability to target a vehicle. A black Firebird with pop-down headlights and no front plate is extremely difficult, if not impossible, to measure. A white car at 1000 feet has 10 times the reflectivity of a black car at the same distance. A large eighteen wheeler with crome bumpers is a sitting duck. Laser's effective range when targeted at the front of a vehicle is approximately 1000 feet. From the rear up to 4000 feet. Rear reception is assisted by the reflectors in tail lights and the square back design of most vehicles.

Laser has several advantages over radar and several disadvantages. Laser can target individual vehicles in a group, radar can not. Radar/laser detectors are of little use when confronted with laser. A detector mounted on the windshield at the traditional aiming distance of laser, ie 800 feet from the fun, most likely will give no alert when the laser is aimed at the front plate. It is outside of the laser's 30" elliptical beam width. Unlike radar with it's scattering microwave transmissions, laser's infrared has no scatter alerting a vehicle trailing the target vehicle with a detector. Laser cannot be used in moving mode, it must be stationary. Most state enforcement agencies have passed on using laser for this reason. Laser is most prevalent in metropolitan areas with one officer on an overpass operating the laser and officers lined up on entrance ramps waiting for the radio to ID the offender. Similar to radar, laser cannot be used in the rain, snow, och high dust envisonments. Laser takes precise aiming, radar does not. Like radar, laser is susceptible to cosine error.

Cosine Error is the angle from the 0 degree perpendicular to the target vehicle. The greater the cosine angle the greater the error. However, cosine error is always in favor of the motorist, ie speed readings will be proportionally less than actual speed of the target vehicle.

Sweep Error is manifested when the laser is aimed at one part of the vehicle, say the license plate, and due to the motion of the operator, the laser also targets a side mirror during the same trigger pull. Sweep Error adds to the real speed of the target vehicle.

Refection Error is next. On very hot days with low humidity a visible mirage/reflection of the target vehicle is created. In many cases, when the laser is aimed at the target vehicle the infrared beam also receives readings from both the target vehicle and the mirage causing a sweep Error.

Overexposure Error is last. When a laser gun receives an extremely powerful refective signal, such as a sunflare off a vehicle, the computer's timeer can not see the return of the 904 nanometer signal it sent. It can not compute a speed reading. In general, the laser gun is looking for the strongest return reflection of its own emitted beam for speed computation.

Countermeasures Radar/laser detector evaluations have consistently reported detector inability of providing advanced warning to police laser guns. Laser citations are going up. In 1996, the Ohio State Police wrote some 107,000 laser citations. Beginning in 1995, the market saw the entry of laser countermeasures from established and new companies. K40 introduced their Laser Defuser, Rocky Mountain Rader announced the Phazer, Lidatek promoted laser Echo and license plate covers touted their ability to thwart laser beams. In late 1996 and early 1997, new laser countermeasures emerged, ie Laser Blinder, Laser Buster, Rocky Mountain Radar's Phantom, Laser Plate, Laser Light, Laser Sun, T3 Alpha Plate, Taylor Bell Plate, TeleRadar/Laser. Car and Driver magazine gave positive reports on Laser Echo and K40's Defuser as products in evolution.

If you own a jammer, how can you test it? Surely you would not go the police department and say, "Officer, I just bought a jammer, would you test it for me?" This has been the problem. Many unscrupulous companies have introduced products designed to take your money and only jam the truth. Speed Measurement laboratories, aka Speed Labs, was asked by several magazines to test these new laser countermeasures for effectiveness and report the findings. Field testing was conducted over a nine month period at three defferent test sites. Guns were operated by state police officers, retired police officers, radar and laser gun representatives, and Speed measurement Laboratories staff.

Field Testing ­ Each laser countermeasure was run at both the LTI 20/20 Marksman and Kustom Pro Laser II laser guns. Test vehicles were driven at 30 mph and 60 mph with the aiming point at determined distances of 1000 and 750 feet from the laser gun. the laser guns were aimed at both the front license plate and the headlights. Drivers counted down "three, two, one" when they reached the aiming point cone and the laser guns were triggered. Test vehicles were in two way radio communication with the laser source. Jamming duration was recorded in both distance and time as measured with stop watches. All jamming devices were assessed compared to what the operator's manual of the particular jamming device said the device would do.

Activities were covered by the Associated Press, NBC, CBS, ABC national and local affiliates. The test activities were witnessed by more than sixty people including the El Paso Police Department, Fort Worth Police Department, Texas Department of Public Safety and various newspaper accounts. The laser guns were operated in accordance with axxepted police practices and consistent with operation manuals of the laser gun manufacturer. Each countermeasure was given three runs at each laser gun in each category. In the case of the Laser Echo and K-40 Defuser Plus, both devices were tested on two separate occasions at two different sites in the same categories.

Conclusions