NewPublicHealth Q&A: Jon Vernick on Helmet and Speed Laws

Sep 1, 2011, 7:27 PM, Posted by NewPublicHealth

Do motorcyclists in your state need to wear helmets? That can depend on the year, according to a recent report from the Centers for Disease Control and Prevention (CDC). According to the CDC, states have cycled from near universal helmet law coverage in the early 1970s, following the enactment of federal highway funding requirements, to a pattern of repeal, reenactment, and amendment of the laws across the decades. The helmet law requirement for federal highway funds was later repealed.

In 2000, Florida reduced its motorcycle helmet law coverage for adults; the following year motorcycle deaths increased by almost 50%. Louisiana weakened its helmet law in 1999, and motorcycle fatalities doubled by 2003. The law was reinstated in 2004, and the number of deaths and severe injuries significantly decreased.

NewPublicHealth recently spoke with Jon Vernick, Deputy Director of Johns Hopkins Center for Injury Research and Policy about the impact of the enacting and repealing these laws.

NewPublicHealth: What do we know about the impact of helmet laws?

Jon Vernick: When you mandate a universal helmet law — one that applies to all riders rather than, say, only young adults — helmet use goes up very dramatically, typically doubling from about 50% to about 95%. On the other hand, when you enact a motorcycle helmet law that’s not universal we don’t see nearly as big an increase in helmet use. The reason is not just that some people aren’t covered, but even for the people who are covered, for the young people, for example, we don’t see as high use rates as we would hope because the law is very hard to enforce. You’re basically turning the police officer into a carnival “guess your age" person who has to ask himself, “is that guy 20 or 21?” And so, enforcement is much more difficult.

And when laws are repealed we see death rates go back up. In Arkansas, they had a 20% increase in death rates, Texas about a 30% increase, and in Florida about a 48% increase when the laws were repealed. And then, when a state reinstates the helmet law, as sometimes has happened, we see deaths come down. It’s bad for public health to repeal and then reinstate a helmet law. We’d rather that you just kept the law in place. But it’s good for research because it makes for a very compelling natural experiment.

NPH: Do states learn from one another?

Jon Vernick: One hopes that that research is contributing to the fact that 20 states and DC have such a law, but it obviously hasn’t persuaded, or at least fully persuaded, the other 30 states. And the reason is that there are other factors at play besides public health. The opponents of helmet laws argue, among other things, that this is a matter of personal freedom, that they should have the ability to accept whatever risk there might be and the state shouldn’t be allowed to tell them what to do.

Early on when states enacted helmet laws people brought lawsuits against the state and said not just that the state shouldn't enact such a law, but they said that the state is not allowed to enact such a law. But the courts disagreed. The courts said you’re not alone in accepting this risk. When you crash on your bike, we have to send out police, we have to send out emergency medical services. If you die, your children may need to be cared for by the state, so you’re far from alone in making this decision.

But, that argument about personal freedom has been compelling in some states.

NPH: Do we know what might be compelling to states to get them not to repeal their helmet laws?

Jon Vernick: Iwould argue that research with regard to increased usage and decreased death rates is important. But I think we need more research addressing the question of why some states choose to have laws that we know work and some states decide not to. I think there may be differences in the magnitude and effectiveness of the lobbying of opponents. I think there are probably states where the proponents of motorcycle helmets are more successful in making their case, whether that proponent is a local advocacy or non-governmental organization or whether the proponent is a state legislator. Sometimes these things come down to personal stories, a legislator who has a constituent who died or was paralyzed in a crash without a helmet, or maybe the legislator had even personal experience themselves as a bike rider.

NPH: Is there a relationship between helmet laws and other traffic laws, such as speed limits?

Jon Vernick: I would argue that these laws are the same in some ways and different in others. They’re the same in that we hear over and over the arguments about personal freedom. “I don’t want to wear a helmet, that’s a risk I should be allowed to accept.” “If I don’t want to wear a seatbelt, I should be allowed to accept that risk.” “A state shouldn’t be in the business of telling me what to do when it doesn’t harm anyone else,” is the argument that we see over and over. But in other ways these laws are different.

Speed limits are the other major area where there has been enactment and repeal of traffic laws. Speed limits have been historically a matter of state concern, but then analogous to what happened with motorcycle helmets, in 1974 the federal government, in response to the oil shock, enacted a law that said to states, you’re at risk for losing some of your federal highway funds if you don’t enact a maximum 55 mile per hour speed limit on interstate roads. Then in a series of laws in 1987 and then again in 1995, the federal government essentially lifted that requirement.

NPH: And what happened?

Jon Vernick: As a result of lifting that requirement, states very broadly repealed their maximum 55 mile per hour speed limit on a variety of different roads.

NPH: And the result has been?

Jon Vernick: According to a 2009 article in the American Journal of Public Health, if you look at the period from 1995 to 2005, there was between a 3 and 9% increase in fatalities attributable to the increase in speed, and that translated to more than 12,000 deaths in fatal crashes and 36,000 injuries. The thing about speed, if one is thinking in terms of injury prevention, is that it’s an especially pernicious risk factor. It’s pernicious because higher speeds increase both the risk that a crash will occur in the first place, by reducing reaction time and increasing stopping distance, and the risk that harm will occur because it increases the crash force. And speed doesn’t increase the crash force just a little. If you remember your basic physics from high school, the kinetic energy varies by the square of the velocity in a crash. So, relatively small increases in speed in a crash are associated with even larger increases in the force of that crash.

Of course, we would all be safest if our cars drove 5 miles per hour, but then we would never get anywhere, and we obviously have to balance our desire to be a productive nation and economy with what level of crash risk we’re willing to accept. The 55 mile per hour speed limit, people grumbled about it, but it dramatically decreased death rates and decreased fuel consumption as well. That’s the primary reason that it was enacted, to decrease fuel consumption and decrease our dependence on potentially unstable sources of oil. And a wonderful additional benefit was the decline in death rates.

This commentary originally appeared on the RWJF New Public Health blog.