Several months ago, I was on a leisurely weekend morning drive, on my way home and feeling mellow. Little did I know, I was driving myself right into a public health debate.
As I approached a downtown traffic light, it turned yellow. With a full line of sight, sparse traffic at a full stop on the other side of the intersection, and no pedestrians, I performed an incident-free rolling left turn. I thought nothing of it until a few weeks later when I opened my mail. Which, might you posit, did I receive?
A letter of acclaim for a safely executed “California Coast” one-way turn? A friendly reminder to come to a complete stop at all signaled intersections? A not-so-friendly notice from some guy in Phoenix offering me an opportunity to appear in County Superior Court?
Anyone who has been snagged by red light camera enforcement knows the correct answer. This experience and its price tag (more than $600 in fines and fees!) inspired me to take a close look at the rapidly growing but controversial practice of using cameras to police busy intersections.
From a public health standpoint, red light camera enforcement has its genesis in the vehicular injury prevention efforts of the 1960s, inspired by Ralph Nader, William Haddon Jr., MD, (the seminal director of the National Highway Traffic Safety Administration), and others. Today, their preventive strategies (like building safer cars) sound like common sense, but American culture wasn't always hip to prevention.
Nowadays, we accept that there are strategies, such as seat belts, air bags, and highway speed limits that prevent or limit injury in car crashes. We recognize that crashworthy vehicles save lives and that vehicle occupant fatalities (per mile of travel) decreased by two-thirds between 1964 and 1990. Without a doubt, this is an incredible public health accomplishment, one that has been achieved with modest impact on personal liberty.
With success like this, it's not surprising that a whole new generation of preventive interventions has been proposed to limit the carnage on our streets. One of these is red light camera enforcement, which strives to limit injury and death from intersection collisions. And I should stress that this is not a trivial problem. According to the Insurance Institute for Highway Safety (IIHS), more than two million intersection-related crashes occurred in 2009, resulting in 7,538 deaths. On its face, though, red light camera enforcement feels more like Big Brother than airbags or widened shoulders. And it is far from being passive protection — it relies on individual citizen's knowledge, fear, and compliance to be effective. This is in contrast to a more automatic strategy, like lengthening yellow light times.
On the other hand, is it possible that a city that utilizes red light camera enforcement increases safety not just at the enforced intersections but across an entire city? This is consistent with James Q. Wilson's “broken-window” theory (embraced by former New York police commissioner William Bratton) that visible disorder in a neighborhood leads to greater lawlessness citywide. It makes sense to take a larger view of the effect of red light camera enforcement. A recent analysis from the IIHS can help us do just that. The report, lead-authored by Wen Hu, compared cities with and without red light camera enforcement programs across two time periods (1992-1996 and 2004-2008). The investigators looked not just at the enforced intersections but citywide to discern differences between those with and without red light camera enforcement.
The authors report a 21 percent greater decline (35% vs. 14%) in fatal red light crashes in cities with camera enforcement than those without it. The investigation also reports an estimated 17 percent decrease (versus expected rates) in fatal crashes at signaled intersections in cities with cameras. This study has a lot of strengths — it is big — looking at 62 U.S. cities (14 with camera programs and 48 without) and focusing on an important outcome (fatal crashes). It also does a reasonable job of creating a nationwide sample, of adjusting for crash rates per 100,000 in population, and of accounting for confounders such as population density and land area. In sum, it is reasonably convincing. But before you start petitioning the local city council for cameras at every intersection, you should know that there are important limitations.
One of these is conflict of interest. The IIHS is funded by the insurance industry, an industry that benefits if there are fewer car accidents and also if more drivers accumulate points on their license (increased fees). But let's give them the benefit of the doubt, and assume they are interested in studying road safety in an unbiased fashion. What then are the limitations of the study?
First, those cities implementing cameras had a higher baseline rate of crashes (65% higher), meaning they had more room for improvement. Secondly, there were significant differences in rates across cities (crashes increased by 165 percent in Raleigh, NC, while decreasing by 75 percent in Chandler, AZ). Third, the control group — those without cameras — had two major outliers whose crash rates more than tripled during the study period. Removing these two cities from the analysis might have led to much more modest results. Fourth, the analysis could not account for changes in yellow light times or other interventions that might have been the true cause of decreased fatal crashes.
Finally, these data excluded crashes from illegal turns on red (the vast majority of red light tickets in most locales are for illegal turns). This study is unable to inform the question of whether policing failure to come to a complete stop on red benefits the public welfare. What does this all mean? In my opinion, it means that the jury is still out on the public health impact of red light camera enforcement.
On the other hand, the jury is no longer in deliberation for my red light camera enforcement citation. To be clear, there was no jury — just an honorable Superior Court judge and a 12-second videotape. My judge was not sympathetic to the plea that a failure to come to a complete stop on red was not equivalent (penalty-wise) to that of busting through a straight-ahead intersection. Oh, well. For other perps and me, we can take heart that our money is not only supporting the local police department (and Redflex Systems of Phoenix, AZ) but also a whole host of public services: $8.92 for the county General Fund, $17.15 to the Criminal Justice Facilities Fund, $13.72 for the Courthouse Construction Fund, $19.60 to EMS, $9.80 for DNA Identification Penalty Assessment, $13.72 to Maddy EMS, $3.43 for Automated Fingerprint ID System Fund, and the list goes on. Sometimes a state budgetary crisis and a public health initiative can become inextricably linked. Public health…just do it?
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Dr. Ballardis an associate emergency physician at Kaiser-Permanente in San Rafael, CA, and the chair of the CREST ED Research Network. His writing credits include co–authorship with Angela Ballard of the award-winning travel narrative A Blistered Kind of Love: One Couple's Trial by Trail (Mountaineers Books, 2003) and authorship of The Bullet's Yaw (IUniverse, 2007). Dr. Ballard writes a biweekly-medical column for the Marin Independent Journal, which he posts on his blog:http://incisionanddrainage.blogspot.comCopyright © 2011 Wolters Kluwer Health, Inc. All rights reserved.