What to consider when operating Lidar

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Before operating a lidar, the officer or operator should first check to make sure each component is with/on the device, as well as in place. The operator should then inspect the device for external damage, missing components, or any damage that could prevent the lidar from functioning accurately and properly. 

Additionally, the operator must carry out accuracy tests prior to using the device in the field. This includes:

  • Internal accuracy check – Light segment and indicators test. The lidar operator performs a light test to ensure all light segments and indicators are functioning properly.  
  • Internal circuit check 
  • External accuracy check – alignment
  • Range accuracy

If there is any issue that could harm permanence, the lidar needs to be immediately removed from operation in the field, and repaired before returning.

Field Operation

Once the pre-operational checks have been made, the lidar device should be transported in the officer’s vehicle. There should be some sort of holster to keep the device in place when the vehicle is in motion, or another method to keep it in place. This method should not obstruct the vision of the officer while driving, limit his or her movement in or exiting the vehicle, and should allow for the device to be easily accessed. 

The device should also be secure enough that injury would not occur from the device in the instance of a crash, or driving in pursuit. It should never be placed in the driver’s lap, in the passenger seat, or anywhere other than the saddle bags in the case of motorcycle use. 

The operator also must develop a tracking history when attempting to use the lidar as a viable piece of evidence in the Vermont court of law. There are several aspects to tracking history, such as:

  • Visual observation – The officer must identify the target, estimate its speed, estimate the distance to the target, and observe the environment.
  • Audio confirmation – The officer must listen to the pitch of the audio from the lidar and make sure it is giving off a target acquisition tone. 
  • Unit confirmation – The lidar must give off steady or multiple readouts that are consistent, and match with a relative degree of similarity, the officers estimation. 

Factors Affecting Lidar Operations

  1. Radio Frequency Interference (RFI) – One way this occurs is through the transmitters of law enforcement radios, walkie-talkies, or business radios. To avoid this, abstain from transmitting radio signals in or around the vehicle while trying to take lidar readings. Another variable that can cause frequency interference is light devices. Certain equipment used for lighting such as mercury vapor, neon, or fluorescent lights can cause interference and the officer should avoid taking readings around these lights. A third variable is electrical lines, which can also cause interference, and the officer should choose a site to operate in that is free from this kind of interference. 
  2. Panning – when the laser is swung quickly past a stationary object, causing an error reading.
  3. Sweep effect – If the operator is striking the target vehicle with the laser from an angle, he or she may strike the back first and then the front, or vice versa. This creates an inaccurate reading, either faster or slower depending on which part of the vehicle was struck first. The officer needs to make sure they maintain a steady aiming point on the target. 
  4. Windshield obstruction – The windshield can limit the range of the device, but will not limit the accuracy. 
  5. Weather – Weather conditions such as rain, smoke, fog, and dust clouds can limit the range of the lidar. 
  6. Low Voltage – If the operator experiences a low voltage incident with the device it should be removed from the field, as this can create unreliable and inaccurate readings. 
  7. Cosine Effect – The larger the angle the lidar is being operated from in comparison to the target vehicle, the lower the speed reading is in comparison to reality. This always works in the motorists favor. For instance someone who is traveling at 70 miles per hour would be perceived to be traveling at 65.78 miles per hour from a 20 degree angle. 

Legal Considerations

Lidar is used by law enforcement in Vermont as a form of evidence at Judicial Bureau hearings. For this evidence to be admissible in court, there must be sufficient reason to believe that the lidar reading was an accurate representation of the speed of the target vehicle, at the time of the alleged violation. Therefore the basic accuracy questions must be asked. Do we know that the operating principles of the lidar were valid? Was it working properly at the time of the alleged violation? Did the operator have the proper qualifications and perform properly? Do we know that the vehicle accused was the vehicle that the reading came from?

It is important to understand how lidar devices are used in the field properly, so that you can challenge the validity of the reading if you believe it was wrong, or you believe the officer was not operating the device properly. Do not allow an allegation backed by false operation to harm your driving record, or cost you money. All speeding tickets are viable to be challenged, and challenging the accuracy of the lidar as well as how it was operated/tested on the day of the allegation is an effective way to clear yourself of any charges or fines. 

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