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3/24/2011
California: Longer Yellow Time Slashes Red Light Tickets
Red light running drops 81 percent at Fremont, California intersection where 0.7 seconds added to yellow time.

Roger JonesAn extra 0.7 seconds of yellow time at a Fremont, California intersection did more overnight to cut violations than a decade's worth of red light cameras use. What was once the city's most profitable photo enforced location now rarely sees any straight-through violations.

Since 2001, the Australian firm Redflex Traffic Systems has mailed out 95,802 tickets -- now worth $476 each -- in Fremont. Last year, $4,765,236 in tickets were sent to vehicle owners, with $923,916 generated at the intersection of Mohave Drive and Mission Boulevard.

That changed once Fremont resident Roger Jones set out to investigate a ticket that an acquaintance of his received in July while turning left 0.28 seconds after the light turned red. Jones found the yellow for the left turn lasted just 3.0 seconds -- the shortest time allowed under federal law. Jones determined that a demand-based signal timing system creates a situation where green times could last as little as 4 seconds during a period of light traffic, trapping a driver approaching to make a left-hand turn.

"This complex series of events created an impossible dilemma," Jones told TheNewspaper. "When the light turned yellow the required deceleration rate would have required a near panic stop rate of deceleration."

The signal in question is maintained by state officials with Caltrans who investigated the complaints. Engineers on the scene disagreed that the left-turn phase provided insufficient yellow, but in the course of their engineering survey they decided other changes were warranted.

"Staff noticed that the yellow for the through movement was 4.3 seconds which is the corresponding yellow for a posted speed of 45 MPH, then, through field observation, they determined that the yellow should be increased and staff increased the yellow to 5.0 seconds," Caltrans engineer Einar A. Acuna wrote in an email to Jones.

One month prior to the yellow lengthening in November 2010, 199 tickets were issued at the location. Since the change, the overall number of tickets has dropped to an average of 71 -- a 64 percent decrease. Longer yellow, however, only affects straight-through violations, not right-hand turns. Excluding the turning tickets, citations dropped from 121 in October to just 23 straight-through violations in December -- an 81 percent decrease.

While a 0.7 second difference in the duration of the yellow warning at an intersection might appear insignificant, the extra margin of safety is critical. The vast majority of straight-through red light "violations" happen when a driver misjudges the end of the yellow light by less than 0.25 seconds -- literally the blink of an eye (view Texas Transportation Institute (TTI) chart). In most cases, a yellow shortened by one second can increase the number of tickets issued by 110 percent, according to a TTI report. Confidential documents uncovered in a San Diego court trial prove that the city and its private vendor, now Affiliated Computer Services (ACS), colluded to install red light cameras only at intersections found to have short yellow times (view documents), thereby maximizing profits.




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