Fremont is proposing to reimburse drivers who collectively received more than 1,000 red-light camera tickets during a period when it inadvertently shortened the time they could cross on yellow signal lights through a couple of intersections.

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A top city official acknowledged that a series of communication and chain-of-command breakdowns between the public works and police departments led to the mistake.

To comply with a state law that would take effect the following month, the city in July 2015 increased the duration of yellow traffic lights at the Mowry Avenue/Blacow Road and Mowry/Farwell Drive intersections from 4 to 4.7 seconds. The new law required that the length of yellow lights be determined by the actual speed of traffic noted in surveys, not the posted speed.

The extra .7 of a second led to a big drop in red-light tickets issued at those intersections.

But when the yellow light time was shaved back to 4 seconds in February 2016, the number of tickets suddenly soared.

In that February, for example, the camera at the Mowry/Farwell intersection caught 383 red-light runners compared to the previous month’s 66 — a roughly 480 percent increase. At the same time, red-light camera tickets issued at the Mowry/Blacow intersection saw a 900 percent spike, from just 14 to 140.

Those numbers stayed relatively high until late October 2016, when the yellow light time was switched back to 4.7 seconds at both intersections.

Who authorized those changes and why is less clear than the raw numbers.

In early February, local news station KPIX reported a spike in tickets issued by the cameras at those intersections after Jim Lissner, a Southern California man who collects such data, pointed it out.

When pressed by KPIX to explain why the yellow light time was shortened, Fremont Public Works Director Hans Larsen said it wasn’t. He said confusion was caused when a student intern erroneously noted in a revisions log on Feb. 1, 2016 that the yellow light’s duration could be shortened based on the latest speed survey results.

But as Larsen and his team later dug into their records, they found that the yellow light time really was reduced as reported, he told The Argus.

He said a traffic consultant working with the city on another Mowry Avenue project apparently saw the intern’s note in the log and shortened the yellow light time. Management didn’t learn about that until this month, he added.

“What we did discover was that there were changes made to the system that weren’t documented, that weren’t reported,” Larsen said.

But it wasn’t the only thing that went unreported. Larsen said that in April 2016, just two months after the yellow light time had been shortened, a community service officer who helps administer the red-light camera program for the police department went to the intersections for a routine signal timing check with a public works engineer.

He said police regularly do such checks to ensure they can testify in court that lights at intersections with red-light cameras comply with state regulations.

In the April check, the officer and engineer found the yellow lights’ time had been reduced to 4 seconds, but neither reported that information to public works management.

During another check late last October, the same pair found the yellow lights at both intersections were still timed at 4 seconds. This time, however, the traffic engineer realized they should last 4.7 seconds so he had the timing changed back to that. The community service officer documented this change in police records, Larsen said.

But the switch back to 4.7 seconds also went unreported to public works management, Larsen said, even though by then police were using the correct figures in traffic court cases.

“I acknowledge that it was our fault,” Larsen said of the changes and the spike in tickets. “We should have known.”

Larsen said it was a “perfect storm” of circumstances that “led to a failure on my part and our leadership in being able to fully understand what’s happening” with the cameras.

“There are some improvements that we need to make, and are making,” he said. The city’s transportation manager, Noe Veloso, now must approve in writing any signal timing changes at intersections with red-light cameras.

Larsen said he also wants to ensure that public works management and staff, as well as the police department, all have the same records.

He said for consistency, the city will eventually change all the yellow times across the Mowry Avenue corridor to 4.3 seconds.

Mistakes aside, Larsen stressed that 4 seconds is still legally defensible because it complies with minimum state requirements for the roadway.

Still, Larsen said the city recognizes “there’s a fairness issue there that needs to be kind of corrected or addressed.”

To that end, the city will work with the Alameda County traffic court system to try and obtain reimbursements for a little more than 1,000 tickets issued at those two intersections during February and March of 2016.

Each ticket costs $490, according to city documents. The city collects $147 per ticket and pays a monthly fee to Redflex Traffic Systems Inc., the Arizona-based company that licenses the cameras. The rest of the money is distributed to various local and state entities, including the courts.

Larsen said the two-month time frame is fair because drivers presumably could have adjusted to the shorter yellow lights after a while. That means the recipients of more than 3,000 other tickets issued during the rest of the nine-month stretch of shorter yellow lights won’t be reimbursed.

How the money will be reimbursed is still unclear, and there’s no guarantee the courts will support the city’s recommendation.