Friday, May 6, 2011

Forest Heights Answers Charges of Camera Inaccuracy… with Plagiarism

The town of Forest Heights has posted their official responses to charges that their cameras are inaccurate, claims which returned to the public attention after defendants successfully defeated many tickets in court using time-distance calculations.   The town's posting claimed that they had seriously and independently investigated the matter. However in fact the posting was in fact copied almost word for work copied from a similar announcement made months early by another town which had faced similar complaints -- even citing the exact same examples from the other town, and copying the same incorrect technical details about how this type of camera works.

A May 3rd posting was made to the Forest Heights’ website stated
SPEED CAMERA PROGRAM VERIFICATION ANALYSIS
Recently some citizens have raised concerns regarding the accuracy of Forest Heights Speed Camera Program that was instituted on May 1, 2010. The Mayor, Council, and Police Chief take these concerns seriously, as it is critical that citizens have confidence that the Speed Camera Program is operating correctly. Over the last week town officials have reviewed public concerns and instituted an independent verification process. Below is an overview of how well the Town’s speed camera equipment operates.

This statement is almost word for word identical to a similar posting which the town of Cheverly made in the summer of 2010 in response to complaints from residents of THAT town about inaccurate speed readings by Optotraffic cameras.  From the Cheverly website:
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. 


We’ve created a document which compares the two towns' postings.  The only things we have changed were the font size and spacing for comparison purposes, the text of the posts is unchanged.  (We have also archived copies of the original web site postings from both Forest Heights and Cheverly to files, and have hard copies, in case either town remove or change their posting).

Perhaps the most interesting bit of plagiarism is Forest Heights’s description of the complaints:
•TICKET PHOTOS DO NOT SHOW SPEED:
One citizen argued that his own tickets images were evidence that proved the equipment was operating incorrectly. According to his measurements the photos indicated his car had only travelled 24 feet between the first and second photo. He erroneously claimed that the elapsed time between the photos was .461 seconds indicating that the car was travelling at approximately 36MPH based on his calculation of velocity as a function of distance over time.

Compared to Cheverly’s:
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.
Yes that's right, they cited the exact same example using almost the same words.  It so happens that none of the tickets from Forest Heights which we have examined had a time interval of 0.461 seconds. All of them were either 0.363 seconds or 0.4s.  It so happens that the speed limit at the Cheverly camera sites is 10mph lower than at the Forest Heights rt 210 site.  .363s is the time it takes to travel 25 feet at 47mph (the intended distance between photos for a vehicle traveling 12mph over a 35mph speed limit) and .462s is the time it takes to travel 25 feet at 37mph (12mph over a 25mph speed limit… the speed limit on Cheverly Avenue).

One could read this and come to the conclusion that when Forest Heights “reviewed public concerns” it did not actually address any of the examples which have been documented at their own camera sites!

The explanation Forest Heights posted is word for word identical to the one posted last summer by Cheverly: “Response: The photos generated by the camera and printed on the citation are never used to determine the speed of the vehicle. As stated above, the photos are taken after the vehicle passes the device in order 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” not a photo as the vehicle approaches the unit, 50 feet prior to passing 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.

Readers, I wish I could express to you how much fun picking this apart is for us.  First, they allegedly “re-reviewed’ examples, yet they didn’t bother to present an example out of the numerous ones which have been documented which was unique to Forest Heights’s cameras?  And strangely enough, their analysis of those photos was WORD FOR WORD IDENTICAL to the conclusions which Cheverly made?

But let’s look at some of the photos.  Hmm no brake lights here:
Or Here:

In addition in our previous analysis of those photos, we looked up the deceleration rates for vehicles of this type and did the math, in at least some of those cases with the largest apparent errors it would not have been possible for a vehicle to have decelerated that much in 50 feet and a fraction of a second.  And, if you look at our second example above, the vehicle was not even fully in frame when the first picture was taken... apparently it had not traversed the full 50 foot expected distance in the time interval before the first image was taken.  So n fact there is an additional time interval and distance involved, the time before the first photo was taken, and the vehicle did not travel the full expected distance during either interval, and the fact that the time and distance available for deceleration is less before the first photo, supports the position that it was not traveling the recorded speed.   Now we are not suggesting that deceleration could not possibly account for some of the images, but it most certainly does not explain this one. 

In both documents, the explanation tries to claim that photos exist only to capture the plate number, and to determine the vehicle is moving at all, and that they cannot be used for speed verification.  OK, apparently the laws of physics and math do not apply to speed camera photos.   In any case, Optotraffic’s own document about their camera states the following: “While the primary evidence for issuing a speeding citation is the calibrated Lane Sensor, the two photos provide the secondary evidence of speeding that is presented to the citation recipient.” and “Since a stationary object is present along with the vehicle, a photographic method also determines speed, guaranteeing fairness”.  Apparently Optotraffic's version of “fairness” means saying camera images can be used to help find someone guilty, but not to exonerate them.

Aside from this, not all of the challenges to the accuracy of Optotraffic's cameras are based on timestamped images, as at least one driver has presented electronically recorded data in his defense of an Optrotraffic ticket as opposed to time-distance calculations.

Both documents provide a description of how the device “works”. 
The speed camera unit used by the Town of Forest Heights, 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 Forest Heights’ Lidar, the equipment is recalibrated daily to ensure the equipment that makes this distance/time calculation is accurate.
Lidar calculates the speed of an approaching vehicle beginning at a point 50 feet prior to the unit, where laser beams strike an approaching target vehicle at two defined locations.


The interesting thing is that this description is TECHNICALLY INACCURATE, according to Optotraffic’s own documents and information from the patent record.  Optotraffic’s units are a proprietary design, and do not measure the speed of approaching traffic the way police LIDAR does.   The measurements are taken downwards onto the road, and actually are measuring the times when the vehicle crosses two laser beams which are a fixed distance apart.  Those laser sensors are pointing “perpendicular to the line of traffic”, according to Optotraffic’s technical documents… when the car is directly below the sensors on the unit.  It is interesting that neither town bothered to get this detail correct.  This oversight in the towns’ explanations gives the impression that the distance between the point when speed measurements are made and photos are taken is farther than it really is…. measurements are NOT made 50 feet “prior to the unit”, they are made *at* the unit.

The explanation continues:
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 then 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) and the second purpose is to prove the vehicle was in motion at the time of the incident. Occasionally it is suggested by the violator that the vehicle is parked or standing. A citation is subsequently issued to the vehicle owner, as required by law, only after it is verified that there is direct visual evidence of the vehicle owner’s registration plate displayed on the vehicle.

Both documents make an identical explanation to an incident in Brentwood, where a large number of citations were refunded due to an administrative issue.  However they fail to address a completely separate issue with that town’s cameras reported by the Washington Examiner, which allegedly involved buses traveling at impossible speeds.

Both documents use identical text to describe how the machines are “calibrated”.
CALIBRATION:
The Optotraffic equipment runs a self- calibration test every morning. An Optotraffic Technician and a Forest Heights Police Officer meet daily at the unit to review the results. Therefore, as standard practice, the equipment is verified every day.

Ok, note the words “self calibration test”.  Let’s be perfectly clear, there is NO ACTUAL SPEED MEASUREMENT TAKEN IN THESE TESTS.  The machine is running a basic diagnostic, essentially that the components are turned on and it can contact the GPS satellites.  The concerns about Forest Heights/Optotraffic’s camera are NOT that the devices are improperly calibrated, is it essentially that the system may have a fundamental flaw which would produce sporadic errors or errors under certain circumstances.  A “self calibration test” would never detect such a problem.

They did at least have slightly different numbers for “Overall Program Results”, with Forest Heights claiming that the 72,808 citations its cameras have issued so far constitute only a tiny fraction of the cars running on Highway 210 and that this shows “the equipment is not generating an abnormal number of tickets.”  Forest Height has a population of about 2600 residents, which would be 28 tickets per resident of the town.  We would further submit that this amounts to about $2.9million in revenue or about $1120 per resident of Forest Height.  While we realize many of the tickets are not going to town residents, the editor of this article, speaking as someone who hasn’t gotten any speeding tickets in the last 5 years, takes issue with the idea that this isn’t an “abnormal number of tickets”.  (Also, credit to a story in ""The Skeptical Juror" blog
for pointing out that the town was also off by their calculation of the percentage of cars receiving tickets, by a factor of 100, and that their assertions regarding the average speed on the road was actually mathematically impossible)

From the Forest Heights report:
INDEPENDENT VERIFICATION:
In order to provide a completely independent verification of the Optotraffic unit’s calibration, Chief Webb has instituted a verification process where he has had officers drive cruisers through the equipment at set speeds. The speed of the vehicle is verified by both the car’s odometer and a hand held radar/laser gun. This process will be repeated at a 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 calibrated annually in order to be valid in any court appearance, and were used to show the town’s speed cameras are accurate

From Cheverly:
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.   
Well at least they changed the police chief’s name!  Assuming that any such verification actually took place at all, we are curious what dictionary Forest Heights was reading when they decided that their doing the test when OVER HALF OF THE TOWN”S BUDGET IS COMING FROM SPEED CAMERA REVENUE .  And assuming any such test did take place, one might question whether a single test under controlled conditions would actually check for the sources of sporadic errors which have been hypothesized.   In addition StopBigBrotherMD.org, and several others, have requested access to records pertaining to camera errors under the Maryland Public Information Act and those requests were denied (in a more recent response to another request, the town stated that they would redact essential technical data from a partially denied request for camera logs and certificates, and refused to allow inspection of timecards for camera operators who signed the logs.)   If the town wants an “independent investigation” how about actually allowing someone who doesn’t have a multi-million dollar stake in the outcome to see your  records?

The residents of the Town of Cheverly did not buy that town's explanation of Optotraffic's camera errors.  We suspect people will not buy Forest Heights' story either.  But perhaps the town's "independent investigation" would have been more credible if they hadn't merely copied their neighbor's homework.

(If you thought our analysis of this posting was amusing, read the story in "The Skeptical Juror" which points out a number of errors and inconsistencies in Forest Heights' posting which we missed")