Scottsdale has thrown out nearly 600 photo enforcement speeding citations after learning they were triggered by a faulty sensor.
The affected motorists were all snapped between Dec. 7 and Jan. 4 in the eastbound curb lane on Shea Boulevard at 120th Street, one of the midblock surface street speed camera locations.
The city received complaints from motorists about the camera flashing when they were traveling below the activation limit.
The cameras are activated at 11 mph above the posted speed limit.
A police investigation showed vendor American Traffic Solutions was issuing 75 percent above the normal number of citations in December from the camera location, Scottsdale police Sgt. Mark Clark said.
"Clearly, there was an anomaly, and we notified ATS," Clark said.
As a result, the city dismissed 589 citations already mailed by Scottsdale City Court, reimbursed 35 motorists who had already paid fines or driving school fees, as well as correcting their driving records, city spokesman Pat Dodds wrote in an internal e-mail Monday obtained by the Tribune.
The affected drivers are receiving notices their citations have been voided, Dodds wrote. Recorded speeding violations from the curb lane that had not yet been processed into citations were also dismissed.
"All were going over the speed limit, but we couldn't verify the exact speed they were going," company spokesman Josh Weiss said.
Weiss said American Traffic Solutions learned of the problem Jan. 4 and shut down the camera site for repair until Jan. 16.
Weiss added the company has since verified all of Scottsdale's surface street and Loop 101 freeway cameras are functioning properly.
"These sensors are used on thousands of cameras, and it's extremely rare for something like this to happen," Weiss said.
The company operates the Scottsdale surface street and freeway cameras. The Scottsdale-based company, which operates in more than 100 communities, including Mesa and Phoenix, took over from previous vendor Redflex Traffic Systems last year.
Dodds said a number of years ago, Scottsdale refunded fines after realizing speeding citations issued by a mobile speed van were done using the wrong speed limit.