Well, it seems that although LIDAR is good at measuring speed and distance, the guns are a bit of a pain to use. Fog, rain, dust, vehicle halogen headlights, movement, (just to mention a few) make the guns more difficult to use than radar. They can't be used inside a nice warm police car either unless the window is down most won't work through glass without error.
When used for distances over 400 yards they usually have to be tripod mounted or steadied to stop beam shake and instability.

With handheld laser, a 1 degree movement of the operator's hand moves the beam 6-7ft for every 100 yards the beam travels from the gun.

Laser speed detection renders radar detectors useless due to laser's tight beam-width (two feet at 800 feet) a radar/laser detector mounted outside the beam's strike-zone will give little or no warning, and thus isolates the most flagrant speeders, however a Laser or Radar Jammer will help if mounted well on your vehicle, some of the systems sold will give you enough time to slow before the next reading is taken, for more info see my links page for more information.

Most Laser Guns measure speed in 1/3 second, not nearly enough time for a driver to react to a laser detector warning.

But to acquire a reading, the laser beam must bounce directly back to the laser gun from a flat reflective surface. Consequently, laser guns are specifically aimed at a vehicle's licence plate or front headlights, and the gun's computer looks for the strongest return signal

Above: Typical printout of an offending vehicle, used for evidence.

Above: Photograph taken on the Northants LTI 20-20 Laser camera.
My Thanks to Bob for this one... £40 and 3 points for 92mph

Calibration: Laser devices are self-calibrating. The device itself performs verification at power on, but the police must also check the device at the start and end of each tour of duty of the device. They often check the device against a patrol car with a calibrated speedometer, referred to as calibration verification. A record of the check must be made - usually in the officer's pocket book. If a calibration defect is found, the unit is returned to the manufacturer. Once a year the calibration is performed by the manufacturer or a certified agent, and a certificate of calibration is issued to the police. A visible sticker showing the date of calibration must be fixed to the device along with lead seals similar to what you would have on your electric meter.

They are being used more and more, either Hand Held, resting on a wing mirror of an unmarked car, or on a tripod with a video camera linked to it for the Video evidence quite often printing out a picture of an offending vehicle. These are usually accompanied by a unmarked car or van. The most common place to site the is on a motorway bridge, usually the small farm crossing bridges. They also have a tendency to site them on bridges in roadwork's, to blend in.

Use of laser guns on a bridge has its own rules, they are to be as close as possible to the centre line of the lane being targeted to reduce cosine effect. They must also carry out a height check from the height of the bridge to the road below and multiply this figure by 10. This then becomes the minimum distance the ACPO allow for speed measurement. For example, if he's on a bridge 9 metres above the motorway, the minimum distance to target a vehicle is 90 metres.

Kent, Manchester and Wales Police do this the most.

Common support vehicles are unmarked vans, but Kent also like Citroen AX cars. On a motorway they set the limit at about 85mph or above.

This is far becoming one of the most common mobile ways to nick you.

Examples of laser guns in use:

Above: Prolaser II in use on the wing mirror. A1 Lincs.

Above: Police using LTI 20-20 in Unmarked Ford, Manchester M6/M62 in a known accident blackspot area.

Above: Police using LTI 20-20 and camera in marked van, note the yellow lights, is that to throw you off the sent. Northamptonshire M1 Jun 15
They don't like you taking pictures, but they have taken pictures of over 18000 offenders in less than three months.

Specifications

Marksman Specifications LTI 20-20

Dimensions: 3.5 in x 5 in x 8 in
Weight: 4.5 lbs
Speed Measurement Distance: 30 ft to 3500 ft
300mts With Video Camera
Speed Maximum: +200 mph to -200 mph (accurate zero reading) Accuracy: +/- 1 mph
Acquisition Time: 0.3 seconds
Range Measurement Distance: 30 ft to 3500 ft Accuracy: +/- 6 inches
Acquisition Time: 0.3 seconds
Targeting
Pin-point beam (3 milliradian divergence, 3 ft wide at 1000 ft)
Adjustable illuminated red dot slight
AutoCapture triggering

Left: ProLaser Gun Right: ProLaser with Camera fitted.

ProKustom's ProLaser II

Standard Features and Capabilities:

Standard Features and Capabilities with Camera

RIEGL LR90-235/P & FG21-P

Left: RIEGL LR90-235/P Right: RIEGL FG21-P

RIEGL LR90-235/P Details

Example of the spread of the Laser Beam over distance. (RIEGL LR90)

RIEGL FG21-P Details

What you see in the display of the RIEGL FG21-P Display.

Left: A lorry shown at 958 metres away, speed 95 km/h heading towards laser gun
Right: A car shown at 937 metres away, speed 114 km/h (- tells the operator that the
vehicle is going away from the laser gun) heading away from laser gun.

He demonstrated on a motorway bridge over the M25 near Sevenoaks, first looking through the camera viewfinder and lining up the tiny red laser dot on the outside lane. An 8mm video recorder in the back of his car is linked to a printer programmed to produce pictures only when he zaps cars doing 90mph and above.
One approached the red dot in his viewfinder and he squeezed the camera trigger. The machine emitted an electronic "bleep" and the printer churned out a picture of a Cavalier doing 91mph. "If people knew the effectiveness of this system, they wouldn't get out of bed," he said enthusiastically. "Earlier this morning I caught 16 motorists in twenty minutes in an East Kent village. They were all doing over 44mph in a 30mph zone."

"Bleep" and he trapped another. "Bleep" and another; each hit costs the driver a £40 fine and three penalty points on his licence. "If I was to target drivers doing 80 and above I would do virtually everybody on the motorway, but that would just clog up the system. People are speeding all the time but you have to be sensible. I am after the really dangerous drivers, people doing 90mph and above. They'll get an automatic fixed penalty. Anyone doing over 100mph will be prosecuted and in most cases disqualified."

"Catching speeding motorists could be as easy as taking candy from a baby, if we had more of these units" he said with a big grin.

He reacted angrily to the suggestion that police time might be better spent catching robbers and rapists than speeding motorists. "Tell that to someone whose child has been killed by a speeding motorist," he said. 'If we were to ignore speeding, more lives would be lost. We have a responsibility to make sure that doesn't happen."

Things they don't tell you about Laser Guns

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 favour of the motorist, i.e. 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 licence 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 reflective signal, such as a sunflare off a vehicle, the computer's timer 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.

A recent court case in the USA has thrown a doubt on the accuracy of the LTI 20-20. At a recess in the proceedings the defendant's lawyer picked up the LTI 20-20 from the courtroom bench and proceeded to aim it at the back wall of the courtroom. To his complete astonishment, the gun registered a speed of 5.4mph. Bear in mind that he was aiming at a wall inside a building. He also noted how difficult it was to maintain his target accuracy by simply hand holding the device, with the registered speed fluctuating between -2.2mph and +5.4mph. A net error of nearly 8mph on a stationary object 20m away!

The defendant managed to successfully prove that not only was the gun too heavy to use to reliably pick out a vehicle at 150metres without a tripod, but that it's technology was fundamentally flawed.

Several US states have now banned the LTI 20-20 due to it being inaccurate
in certain conditions......... More Here.