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California: Audit Finds Split-Second Yellow At Red Light Camera Intersection
Audit finds a malfunctioning Sacramento, California red light camera intersection had a 0.05 second yellow time.

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Red light camera opponents often charge municipalities exploit intersections that have dangerously short yellow times for the purpose of issuing tickets. An outside audit of the Sacramento, California red light camera program confirmed that tickets were issued at an intersection where the yellow warning period on occasion flashed by faster than the eye could see.

The transportation consulting firm Iteris conducted a spot check of the 22 intersections where red light cameras were in use in the city and county of Sacramento over a 24-hour period last year. Though the city had audits performed when the program was new, the cameras have not had an independent review in the past six years.

"Because the Redflex equipment collects the yellow (amber) time from the controller output rather than from the programmed time in the controller, the city of Sacramento had requested a review of the yellow interval to determine if there are any discrepancies between what is programmed and what is being outputted, as well as any deviation per output," the report explained.

According to the traffic controller, the intersection of Mack Road and Valley High Drive was supposed to provide 4.7 seconds of yellow. The Redflex camera system reported seeing yellows as short as 0.056 seconds on July 11, 2012 at around 9:30am. The short yellow kicked in during at least eleven signal cycles. The rest of the intersections were found to be within 0.05 seconds of the programmed time.

The audit also revealed that city intersections provide yellow signal timing between 0.1 and 0.4 seconds shorter than the county provides under identical conditions. The county also gives motorists more warning by calculating speed limits based on the 90th percentile speed of motorists, while the city uses the lower, 85th percentile figure. The auditors found a few locations did not even meet the legal minimum yellow time specified in the California Manual on Uniform Traffic Control Devices. The county specifies a 5.1 second yellow for a 60 MPH intersection, which is 0.3 seconds shorter than the legally required minimum under the state MUTCD.

The report recommended the city and county come into compliance with the law and continue having regular independent checks on the cameras and signal timing. It also chided officials for not trimming trees when the limbs hide the cameras and legally required warning signs.

A copy of the audit, courtesy of, is available in a 3mb PDF file at the source link below.

Source: PDF File Automated Red Light Running Enforcement Engineering Audit (Iteris, 11/6/2012)

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