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Speed Camera Program Verification Analysis
Speed Camera Program Verification Analysis
A few residents have raised concerns regarding the accuracy of Cheverly’s Speed Camera Program that was instituted on June 17, 2010.  The Town Council, Town Administrator and Police Chief take these concerns seriously, as it is critical that residents have confidence the Speed Camera Program is operating correctly.  Over the last 10 days town officials have reviewed resident concerns and instituted an independent verification process.  Below is an overview of how the speed camera equipment operates and the elements of the Town’s review.  
How the equipment operates: The speed unit used by the Town of Cheverly, supplied by Optotraffic, utilizes Lidar technology for speed detection coupled with a camera for capturing vehicle information.  Lidar is a speed detection technology that utilizes a laser beam to determine the distance to the target vehicle by calculating the time it takes for the beam to reflect off of the vehicle and return to the unit.  As a vehicle approaches the unit the distance changes, the change in distance and time are the variables used to determine the target vehicle's speed.  In the case of Cheverly’s Lidar, the equipment is recalibrated daily to ensure the equipment that uses this distance/time calculation is accurate.
Lidar calculates the speed of an approaching vehicle beginning at 50 feet prior to the unit, when laser beams strike an approaching target vehicle at two defined locations.  When the unit calculates the speed of a violator, and determines the speed is in excess of 12 mph above the posted speed, two different camera photographs are made of the target vehicle after it passes the unit. These photographs are not used to calculate the speed of the vehicle, but are used for two essential purposes. The first is to capture the rear registration plate number of the vehicle (since not all States require a front plate). The second purpose is to prove the vehicle was in motion at the time of the incident, and not as occasionally suggested by a violator, parked or standing. A citation is subsequently issued to the vehicle owner, as required by law, only after there is direct visual evidence of the vehicle owner’s registration plate displayed on the vehicle.  
Elements of the Town’s review:
  • Calibration: The Optotraffic equipment runs a self calibration program every morning.  An Optotraffic official and a Cheverly Police Officer meet daily at the unit to review the results.  Therefore, as standard practice the equipment is verified every day.  
  • Overall Program Results: Since its inception the speed camera program has issued a total of 421 tickets, which is an average of less than 23 a day for the 5 weekdays during the 4 weeks it has been in operation.  Based on previous measures, more than 2300 cars travel on Cheverly Avenue each day.  This means that less than .08% of cars have received tickets for exceeding the speed limit by more than 12 mph.  Clearly this does not verify the results of a specific ticket, but it does indicate that the equipment is not generating an abnormal number of tickets.  
  • Ticket Photos: One resident submitted their ticket as evidence that the equipment was operating incorrectly.  According to their measurements the photos indicated their car had only travelled 24 feet between the first and second photo. The elapsed time between the photos was .461 seconds indicating that the car was travelling at approximately 36MPH based on the calculation of velocity as a function of distance over time.
Response: The photos generated by the camera are never used to determine the speed of the vehicle.  As stated above, the photos are taken after the vehicle passes the device because of the need to capture the license plate of the vehicle, and to prove the vehicle was actually moving if it is needed in court.  The speed of the vehicle is calculated by a “laser” as the vehicle approaches the unit, 50 feet prior to the unit.  

The Town’s officer in charge of the program has re-reviewed many of the tickets issued and has noted that many of the vehicles have applied their brakes by the time they have entered the picture zone.  This is one reason the pictures cannot be used to determine the speed of the vehicles.  

  • Brentwood Issues: Some citizens raised the fact that Brentwood had rebated all tickets issued between June 24th and July 13th.  Many believed this was due to a problem with the Optotraffic equipment.  
Reply: We have checked with the Chief of Police of Brentwood and there was an administrative issue with the handling of tickets by the Brentwood staff.  This was not a systemic Optotraffic issue.  

  • Independent Verification: In order to provide a completely independent verification of the Optotraffic unit’s calibration, Chief Robshaw has instituted a verification process where he will drive cruisers through the equipment at set speeds.  The speed of the vehicle will be verified by both the car’s odometer and a hand held radar/laser gun.   This process will be repeated at regular basis.   We have the results of the Chief’s first test and it verified that the hand held radar/laser speed gun is in sync with the laser being utilized by the photo enforcement program.  The Town’s hand held radar/laser speed guns are certified as well on a regular basis in order to be valid in any court appearance.    

 
Cheverly Executive Offices:   6401 Forest Road, Cheverly, MD 20785  (301) 773-8360
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