Red light cameras have been issuing tickets in San Francisco, California for more than a decade, but their impact on safety has been mixed. Earlier this year, the San Francisco Municipal Transportation Agency released its annual report on automated ticketing. While the document claims red-light related collisions throughout San Francisco dropped after photo enforcement began, a closer look at the data shows other engineering factors are at work.

"Red light running collisions have shown a general decrease since the early 1990s, with 2011 recording the second lowest annual total in ten years," the report explained. "Signal hardware improvements funded by the city's transportation sales tax have helped reduce these types of collisions, most notably in the South of Market area. This drop coincides with the city's deployment of red light photo enforcement starting in the late 1990s. Other global factors such as education, motor vehicle design, or demographic changes could also be contributing to these trends."

Intersection by intersection statistics show that improvements such as increases to the yellow signal time, signal upgrades, addition of an all-red period, pedestrian signals and dedicated turn arrows all had significant impacts. The role of cameras is muddled at several intersections where automated ticketing machines were installed after these upgrades were made.

At the intersection of First Street and Folsom Street, for example, cameras were installed in 2000, after a yellow signal increase and signal upgrade in 1998. There was one collision in 1999, the year before camera installation. In the subsequent 13 years, there were an average of 1.2 injury broadside collisions per year. At Sixth and Bryant, injury broadside accidents disappeared in 2000 after the yellow signal timing was increased. In 2001, cameras were installed and the trend continued.

At Fourth Street and Howard Street, there were no injury broadsides in 1996, 1998, 1999 or 2000. Major signal upgrades were made, then cameras were installed in 2004. The trend of either zero or one accident per year continued.

At intersections such as Ninth Street and Howard Street, the agency added a red light camera to an intersection approach where there had not been an injury broadside recorded in the previous eight years, so there could not possibly be a safety benefit to the installation. Marina Boulevard and Lyon Street provides a more egregious example. In the nine years prior to the camera's installation in 2004, there had been only one red-light accident. In the nine years after the camera was installed, there was a single accident. No engineering improvements were made at the location until 2012.

While the safety benefits are unclear at best, the financial benefits are unmistakable. The agency's for-profit vendor issued 15,178 tickets worth $7.5 million last year. A little over 8.5 percent of the citations were challenged and thrown out in court. Although legally required to report the number of tickets issued for right-hand turns on red, the agency refused to release the information, claiming it is unavailable.

"Our vendor, Xerox, does not track whether a violation involved traveling straight through the intersection, turning right, or turning left," the report claimed.

A copy of the report is available in a 500k PDF file at the source link below.