Red light cameras save lives. Photo speed cameras probably don’t.
From 2001 to 2019 the City of Phoenix set up a handful of red-light cameras at strategic intersections with frequent violent crashes. The city council discontinued use of red-light cameras in ’19 because of concerns about “privacy, effectiveness and discrimination”.
The police department is now considering asking the Council to reinstate that authority. Data collected by Phoenix PD suggests that the 12 cameras that had been used prior to 2019 resulted in a 31% drop in red light running crashes at the cross-streets they were used and a 57% drop in red light running crashes in the directions the cameras were facing.
Red-light cameras could return to Phoenix to help police
The Department is considering several proposals. Some are evidence-based, but some aren’t.
- Red-light running cameras (evidence-based)
- Speed cameras at green lights (NOT evidence-based)
- Fixed midblock speed cameras posted on long stretches of road (not evidence-based)
- Portable speed towers (not evidence-based)
- Mobile speed vehicles (not evidence based except around schools)
What’s the public health evidence?
A landmark study for photo enforcement was done by Retting et.al. and published in the American Journal of Public Health examining the impact that photo enforcement had in Oxnard CA after they implemented their photo enforcement program.
Intersections that had red light cameras installed had a 29% reduction in injury crashes. Right-angle crashes (which often happen because of red light running) were reduced by 32% and right-angle crashes involving injuries were reduced by 68%. Overall accidents at the intersections were reduced by 7%.
There is less clear evidence that speed cameras are effective public health interventions. There’s almost nothing in the literature that I could find one way or the other for speed cameras.
However, a few years ago a research team that included Dr. Chengcheng Hu, director of biostatistics for the Phoenix campus of the UA Mel and Enid Zuckerman College of Public Health, Dr. Steven Vanhoy, a recent graduate of the UA College of Medicine – Phoenix, and several colleagues from Banner – University Medical Center Phoenix, offers some insight.
The researchers examined crash data along a 26-mile segment of Interstate-10 in Phoenix where speed cameras had been placed every 2 miles as well as a 14-mile control segment where no cameras had been deployed.
They compared crash data from Jan. 1 to Dec. 31, 2009 (when cameras were in place) to data from Jan. 1 to Dec. 31, 2011 (after the cameras had been removed). They found that the removal of the photo radar cameras was associated with a two-fold increase in admissions to Level 1 Trauma Centers from car crashes in the areas where the cameras were removed.
Nobody likes getting a traffic ticket, but photo red light enforcement can significantly reduce severe injuries if placed in the right intersections. There’s less evidence that photo speed enforcement works, and when used as a revenue generating tool (as it is in Paradise Valley) undermines public support for photo enforcement as a public health intervention as a whole (e.g. photo red-lights).
