Quick Release: WABA Blog Front Page

Why Maryland’s Proposed Helmet Law Would Make Cyclists Less Safe

On Tuesday morning, the Environmental Matters Committee of the Maryland House of Delegates will hold a hearing on House Bill 339 to require that every person operating a bicycle in Maryland wear a helmet. This bill is bad policy.

Mandatory helmet laws cause fewer people to bicycle, and when fewer people bicycle, cycling becomes less safe. So much less safe, in fact, that decreased ridership increases the individual cyclist’s risk of injury more than wearing a helmet decreases risk of injury.

This does not mean that bicyclists should not wear helmets. We encourage bicyclists to wear helmets. However, there are several reasons why people who are deeply committed to bicyclist safety oppose mandatory helmet laws.

Mandatory helmet laws decrease ridership
Numerous studies of places that have enacted helmet laws have shown this to be true. The most commonly-cited study—Dorothy Robinson’s “No Clear Evidence from Countries that have Enforced the Wearing of Helmets”—examined data from New Zealand, from Nova Scotia, Canada, and from several states in Australia. In each place, the mandatory helmet law significantly decreased ridership, from 20% to 44% with an average of 37.5%.

(One can debate whether Maryland can expect a decrease of this magnitude. There is no local data available, so this analysis uses the average of 37.5%. But even if the decrease is only 20%, the lowest Robinson observed, even half of that, the result is the same.)

Lower ridership makes bicycling less safe.
We are defining “safety” as the likelihood of a bike-auto crash. By saying that decreased ridership makes bicycling less safe, we mean that a decreased rate of bicycling within a population is correlated with increased crash rates, and vice versa.

The leading article on this topic—Peter Jacobsen’s “Safety in Numbers: More Walkers and Bicyclists, Safer Walking and Bicycling“—reviews data on biking, walking, and injury rates in 68 California cities, 47 Danish towns, 14 European countries, and the United Kingdom.

Across the independent sets of data from these many jurisdictions, Jacobsen finds a consistent, inverse, curvilinear relationship between bicycling and injury rates, determining that “the total number of pedestrians or bicyclists struck by motorists varies with the 0.4 power of the amount of walking or bicycling respectively.” Expressed simply, more people biking leads to fewer per capita crashes while fewer people biking leads to more per capita crashes.

Jacobsen also derives a formula for how this affects the individual cyclist: “Taking into account the amount of walking and bicycling, the probability that a motorist will strike an individual person walking or bicycling declines with roughly -0.6 power of the number of persons walking or bicycling.” In other words, as more people bicycle, the per capita risk to each bicyclist of a crash decreases; if fewer people bicycle, the per capita risk to each bicyclist increases.

Helmets do not make cyclists as safer as commonly thought
For the individual, of course, the story is different. Wearing a helmet is likely safer than not wearing one. This is true for bicyclists; it is also true for people who are skydiving, rock climbing, sitting under an oak tree, or taking a bath. Individually, we make our decisions based on our own risk tolerances and values, and many of us choose to wear helmets and encourage our loved ones to do so.

But at the broader level, where we ought to analyze legislation and public policy, how much safer will a helmet make a person in a bike crash that leads to a head impact? This is a topic of debate and uncertainty, but as research methods improve we move further from some of the magical thinking that took hold due to early estimates—derived from emergency room data rather than population data—that suggested helmet effectiveness rates of 85% and above.

Generally, those estimates came from retrospective studies that looked at people with head injuries in emergency rooms and compared the numbers who lived and died, and whether they were wearing helmets when they were hit. When more recent studies have attempted to compile these data into meta-analyses with more informative sample sizes, their results do not approach the long-accepted 85% level. Some show a smaller effect; others, none at all. In fact, in population-level studies focusing on hospitalization rather than emergency room visits, helmets have no discernible, statistically significant effect on hospitalization rates. (Jacobsen 2012)

Recent studies that have focused on overall health, rather than simply crash mortality rates, have shown that the individual and public health benefits grossly outweigh the costs, by a factor of 20:1. (De Jong 2012)

The mandatory helmet law in Maryland will increase danger for Maryland cyclists
Assuming that the helmet law will decrease cycling by the 37.5% average in Maryland, the total Maryland cycling population, post helmet law, would shrink to only 62.5% of the current cycling population. Assuming also that Jacobsen’s safety-in-numbers effect holds true in Maryland—as it has consistently throughout California and across Europe—the number of motorists colliding with people bicycling will increase by roughly 17.1% per capita (1-0.6250.4=0.171)

For the individual, these assumptions mean that the likelihood of injury from a crash with a motor vehicle would increase by roughly 33% (0.625-0.6=1.326)—regardless of whether the individual wears a helmet. The increased risk comes solely because mandatory helmet laws take people off bicycles, and fewer people on bicycles makes the remaining bicyclists less safe. Substantially.

Maryland does not keep much data on bicycling, but one piece of data that we do have is that in 2010, there were 734 reported bicycle crashes in Maryland. Looking only at this data—and assuming ridership decreases by 37.5% from the helmet law in Maryland—we might expect only 459 crashes instead of 734.

However, this expectation is wrong. Due to the decreasing “safety in numbers,” we would instead expect to see 537 crashes, or 78 additional crashes directly attributable to the mandatory helmet law. So even though the total number of crashes might decrease, that is not because the law has made cyclists safer; it is because substantially fewer people are riding bikes, and those that still ride are measurably less safe, because of the law.

Discouraging cycling runs counter to Maryland’s other priorities
The state of Maryland has launched, or is poised to launch, two programs dedicated to encouraging cycling. The mandatory helmet law would undermine the success and safety of both.

First, knowing the overall benefits of biking to public health and well-being, transportation, economic development, and other public priorities, the state of Maryland initiated a campaign to get more people riding bikes. Maryland’s Department of Transportation introduces the campaign on their website with:

Governor O’Malley’s Cycle Maryland initiative is an effort to encourage more Marylanders to get out and ride, and to make bicycling a true transportation alternative. Cycling is a great way to connect to your community, support a cleaner environment, encourage a healthier lifestyle, reduce household transportation costs and enjoy Maryland’s magnificent landscape.

With the mandatory helmet law reducing ridership, Maryland will be left with more people to figure out how to move, and will have to treat more people for health problems associated with sedentary lifestyles.

Second, Maryland has contributed funds to expand the popular and successful Capital Bikeshare program to Montgomery County. Due to the nature of bikesharing, users are less likely to wear helmets, more likely to be casual rather than experienced users, and more likely to be operating in urban environments with motor vehicles. So perhaps the legislators proposing this mandatory helmet bill mean to ensure the safety of those riders, before bikesharing arrives in the state?

However, again, consider the data: Capital Bikeshare users have logged over 3.4 million trips, with an approximately 38% lower helmet usage rate than the general population. (Kraemer 2012) There have been zero fatalities and only one head injury. That is roughly one crash for every 88,000 miles ridden! Yet by driving potential cyclists away, a mandatory helmet policy would undermine the likelihood of success of the program in Montgomery County, Baltimore, and other areas statewide.

That safety record speaks for itself and shows that biking is not an inherently dangerous activity. Mandatory bicycle helmet laws falsely portray it as such, and in doing so create a false sense of danger that limits ridership and undermines the many positive impacts of mass cycling for Maryland.

“Contributory negligence” makes the law especially harmful
And finally, some believe that this law is acceptable and benevolent and will not have these impacts because there is no fine for violation. But this law has other, even more dire consequences for violators.

Maryland, like the District and Virginia, is a “contributory negligence” jurisdiction. That means if the victim of a crash contributed in any way to her own injury, she can claim no civil recovery for her damages. In Maryland, violation of a law is negligence per se.

Thus, it is possible that a cyclist who rides the bus to work on a rainy morning but chooses to take a bikeshare bike home when the weather clears, and suffers permanent brain injury when a drunk driver veers into a bike lane and strikes her, could be denied any civil recovery as a result of not wearing a helmet.

Is this the transportation future we want in Maryland? Is this the sort of public policy we hope to encourage?

In Maryland, we can anticipate a mandatory helmet law to reduce bicycle ridership by 37.5% (along with its accompanying public health, environmental, and economic benefits), per capita crashes to increase by 17%, and the per capita risk of a crash to increase by 33% for every person riding a bike in the state of Maryland, regardless of whether he or she wears a helmet.

In a broader sense, these laws are a form of victim blaming—telling bicyclists that it is our responsibility to avoid the risk of injury by padding ourselves, rather than the state’s to design a transportation network capable of moving non-motorists with a decent level of safety and efficiency.

WABA opposes a mandatory helmet law in Maryland because it is bad policy based on accepted, tested, and peer-reviewed data—not just some libertarian philosophy or desire of cyclists to “feel the wind in our hair.”

Fundamentally, we do believe that the legislators proposing this mandatory helmet law hope to do what is best for bicyclist safety, but they have significantly erred in determining what will, in fact, be best. They have the power to impose new risks on each of us who rides a bike, even when we wear helmets. We hope they will consider this information seriously and decide that a mandatory helmet law is a bad policy for the state of Maryland.

If you’d like to voice your opposition to Maryland’s House Bill 399, you can do so here.

De Jong, Piet. 2012. The Health Impact of Mandatory Bicycle Helmet LawsRisk Analysis. 5 (32): 782-790.

Jacobsen, Peter L. 2003. Safety in Numbers: More Walkers and Bicyclists, Safer Walking and BicyclingInjury Prevention 9 (3): 205-209.

Jacobsen, Peter L. and Harry Rutter. “Cycling Safety” City Cycling. Ed. John Pucher, Ed. Ralph Buehler. Cambridge: MIT Press, 2012. 141-156.

Kraemer, John D., Jason S. Roffenbender, and Laura Anderko. 2012. Helmet Wearing Among Users of a Public Bicycle-Sharing Program in the District of Columbia and Comparable Riders on Personal Bicycles. American Journal of Public Health 102 (8): e23-e25.

Robinson, Dorothy L. 1996. No Clear Evidence from Countries that Have Enforced the Wearing of Helmets. British Medical Journal 332 (7543): 722-725.

This post is crossposted on Greater Greater Washington and Baltimore Velo.

Photo by Richard Masoner / Cyclelicious on Flickr


I still believe that you should always wear a helmet when you ride a bike. I know from experience that it can help. What if you didn't wear one and that one time you happen to slip up, hitting your head. You could possibly die because it doesn't take that much with head injuries. My brother got a lot of money after he had a serious head injury in a car accident. He talked to an injury lawyer at http://lawyerfrederickmd.com/Criminal-Defense-Frederick-MD.html and I think it really helped him. It's your choice, but I know I am always going to wear a helmet from now on. 


I was living in Maryland when I first went car free. It was in Takoma Park where I fell in love with a walkable and bike-friendly lifestyle. I almost always wore a helmet.


But if we were to mandate helmets for every activity that carried a head injury risk equal to or greater than the risk that cycling poses, we would also be mandating that helmets be used when people climb stairs, play tennis, walk, ride or drive a car and many other common activities.


The fact that this legislation is being considered is a victory for those who benefit from the exaggerated perception of the danger of cycling.


Have the legislators sponsoring HB 339 demonstrated why helmet legislation is needed? I see that in 2009, 10 of about 550 -- or less than 2% -- of Maryland traffic fatalities were cyclists.


From the De Jong article you reference as peer lit:


"Thompson et. al. (21) review, reference anddiscuss the effectiveness of helmets in preventing head injuries – see also Attewell (22) and Robin-son (13) . Their summary finding is “ ...wearing ahelmet reduced the risk of head or brain injuryby approximately two-thirds or more..."Many motorcyclists dislike helmets. (21) It is safe to ASSUME the same is true for bicyclists. Thus a mandatory bicycle helmet law WILL, IF ANYTHING, reduce cycling. Drops in cycling MAY also result from helmets and helmet laws instilling an exagerated perception of the risks of cycling.[emphasis added]


and the BMJ article you ref is also, as noted in its title, largely INCONCLUSIVE about the effects of dampening ridership overall - yes in some cases BUT there is NO CONTROL for ridership styles, helmet adherence, risk etc.(Do helmeted riders rider more or less riskier, do the drivers treat helmeted riders differently etc.). But importantly, AGAIN it points out there is a SIGNIFICANT reduction of injuries as well the extreme nature of those that did happen, noting helmeted riders ALSO adhere to road rules more, for example. 


So, I won't say you've cherry-picked the data but it's not particularly objective as it's laid out either. Helmets might be a barrier to some but the solution isn't to say we don't need them. That would be like "We shouldn't have seat belts in cars because OTHER drunk people shouldn't be on the road" The REALITY is there IS RISK and public health is about RISK REDUCTION when it's practical. So reducing barriers TO HELMETS is a sensible and cost effective solution - not saying we shouldn't wear them because it limits ridership.


On the other hand a commentator in the BMJ notes, rather sarcastically but effectively, that pedestrians haven't been suggested to wear helmets yet there is risk when they walk about, into traffic and crossing streets etc. (Cinch, P. BMJ. 2006 April 8; 332(7545): 852–853. ). BUT there are mandatory laws about not walking into the bloody street now too aren't there? So the WABA's stance on this is wrong-headed. It doesn't adequately address the risk differences for those who DON'T want to wear helmets might be riding and those who DO want to -it's not been proven EITHER way.


To call this "data-driven" as supporting the rejection of this law is then misleading. That said recognizing the barriers that DO exist and removing them to WEARING helmets should be the focus here - not a rejection of a CLEARLY DEMONSTRATED BENEFIT for when you DO wear one.I can find NO evidence that says wearing a helmet makes health outcomes worst - choosing not to wear one because it's not comfortable is DeJong's financial cost assessment stance but it's hardly solid work - as he states CLEARLY when he says:


" These data suggest that the effect of legislation is to reduce bicycle riding by 20% to 40%. The permanence of any reductions is subject to debate." Fairly he notes that unintended health costs seem to outweigh the benefits of a mandatory law (reduced health when people don't ride, for example)


But he concludes, the FIRST line of his conclusion reads:


"Using elementary mathematical modeling and parameter estimates from previous studies, LEADS TO REASONABLE BOUND FOR A NET HEALTH IMPACT of a mandatory bicycle helmet law."and"A (positive) net health benefit emerges only in dangerous bicycling environments under optimistic assumptions as to the efficacy of helmets and a minor behavioral response."


Put then as... When the environment is unsafe to ride then it IS efficacious to have mandatory bicycle helmet laws because they DO show POSITIVE health outcomes.


So when WABA refuses to advocate for a proven method of reducing public harm they are just wrong-headed. Yes the environment is unsafe and yes focus ought to be on that. But UNTIL THEN you cannot advocate against something that would otherwise keep people from being harmed - it's patently absurd.


Andrew Timleck, MPH (Health Behavior and Health Education), PhD.Baltimore, MDCommuter, Road and Mountain Bike racer etc. (Cat II, NORBA, etc.)


@cyclelicious So if only 10 people died in fires there shouldn't be smoke detector laws because it's not that many people? I'm only trying to push this discussion because these aren't great arguments and if you make them legislators will bury your argument - they'll see your point but also point out the logic flaws. WABA and others need to make a strong case for not making bad legislation - that might mean acknowledging more of the gray here rather than absolutes. Because THAT'S where you'll beat them at the same game.


 @baltobikeboi "Helmets might be a barrier to some but the solution isn't to say we don't need them."


But WABA isn't saying we don't need them. They're saying we don't need to mandate them. 


"So reducing barriers TO HELMETS is a sensible and cost effective solution - not saying we shouldn't wear them because it limits ridership."


WABA isn't saying "we shouldn't wear [helmets] because it limits ridership." They're saying the government shouldn't mandate them because it limits ridership.  I would say you keep missing this important distinction, but you're clearly too smart for that. You must be willfully trying to misrepresent WABA's position. 


"BUT there are mandatory laws about not walking into the bloody street now too aren't there? So the WABA's stance on this is wrong-headed. "


No. There absolutely aren't. Where can you walk to without eventually going into the street? What are crosswalks for? Being so wrong on this completely destroys the statement that follows.  


"To call this "data-driven" as supporting the rejection of this law is then misleading."


You haven't presented anything that comes close to drawing this conclusion, because you've blatantly ignored WABA's position and how they use the data to support it.


"I can find NO evidence that says wearing a helmet makes health outcomes worst"


I don't think WABA has either, but that's OK, because that - AGAIN - isn't the bloody point.  


"When the environment is unsafe to ride then it IS efficacious to have mandatory bicycle helmet laws because they DO show POSITIVE health outcomes."


You're misrepresenting DeJong's conclusions. It is (1) When the environment is unsafe to ride (2) under optimistic assumptions as to the efficacy of helmets and (3) a minor behavioral response THEN it is efficacious to mandate bicycle helmets.


Look, you want to criticize the science or numbers, that's cool. I welcome it. But it is the height of hypocrisy to accuse WABA of cherry-picking data while simultaneously brushing over critical parts of the conclusions you're relying upon. Those caveats about "optimistic assumptions" are critical. You ignored them.  


"when WABA refuses to advocate for a proven method of reducing public harm they are just wrong-headed."


Really? Mandatory helmet laws are a proven method of reducing public harm? If you have such proof why have you not produced it? You're own evidence shows that the claim is at best speculative and only under optimistic assumptions.  It amazes/frightens/embarrasses me that someone with such a light grasp on the facts, arguments and discussion can actually be a PhD and MPH. I guess there are some things (integrity for example) that you just can't learn.


 @baltobikeboi "Drops in cycling MAY also result from helmets and helmet laws instilling an exagerated perception of the risks of cycling."


That was once said of safety glass and set belts on automobiles.


 @baltobikeboi " But UNTIL THEN you cannot advocate against something that would otherwise keep people from being harmed - it's patently absurd."


Yes, they can - and should...for the reasons stated therein. For all of the fancy letters after your name, and the bragging about being a Cat II, you completely miss the point it seems, as to why it's bad public policy to mandate under the force of law that all cyclists, regardless of whether or not they hold some silly USCF categorization, have to wear a helmet. Talk about not seeing the forest for the trees. Fail.


Btw... Think about smoke detectors... Since they became mandatory there are many programs that help reduce the barriers to having them... So focusing on including provisions or, for example mandating routing funds to a program to provide them for low-income persons, etc. is a more comprehensive approach that acknowledges the subtleties in the problem we're all trying to address here.


@Wash_cycle thanks for shaping my opinion of folks from WABA.... You don't see me making personal attacks on anyone here. So putting the personal sleights aside ...you make some valid points. But I still come back to the general and incorrect focus that WABA is pushing about a reduction of over 30% because of a mandatory helmets law. That's not what the research shows when they also point out that these research points have questionable pre and post measures. As for proofs see the bikemore fb page... I gave up posting here since some folks refuse to hear anything but what they want to hear... It's a little more civilized there so if you want the evidence it's there... You've apparently better research and integrity than I so go find it. Good luck. And try to be less amazed/frightened etc. and a little more civil huh? Regards.


 @TimothyNohe  @baltobikeboi Yeah, but they weren't exaggerating the risks of driving... it's extremely dangerous.  Biking isn't, even w/out a helmet.


 @jdanek007  @baltobikeboi 

Look Ms. Jane - if WABA wants to tout that it's using data and the data is faulty then their argument is moot - I only put the letters and my full name because if you hunt around you'll see I advocate for health and well being and am not afraid to put my name to what I have to say. Find a **logical** hole in what I critiqued and then you can write "Fail" - In the meantime a gross lack of "head in sand" is FAIL in its own right. As for forest for trees you can't ignore the bloody trees either or you run into them. Good luck with your fight.


 @baltobikeboi  @Wash_cycle  @Adam  Sorry, but that is only evidence that helmets are a proven method of reducing public harm. It is not proof that helmet LAWS are a proven method of reducing public harm. And a helmet law is what we are discussing here. 


@Wash_cycle this is getting old... Adam Hu wrote: Adam Hu Andrew Timleck, I would suggest reading this meta-analysis of Thompson et. al and Attwell's conclusions before you state that helmets are a proven method of reducing public harm. http://www.cycle-helmets.com/elvik.pdf Beyond that, I think it is fairly easy to advocate against something* that would otherwise keep people from being harmed - if that something* would have unintended consequences that would negatively impact the public health at a greater rate than the potential public health danger being mitigated by that something*. *Helmet law I wrote, taking from there: Andrew Timleck @Adam Hu - thanks for the link ... And for largely supporting my case (I'm teasing ok... But it's still there...) they say : Discussion Do bicycle helmets reduce the risk of injury to the head, face or neck? With respect to head injury, the answer is clearly yes, and the re-analysis of the meta-analysis reported by Attewell et al. (2001) in this paper has not changed this answer. As far as facial injury is concerned, evidence suggests that the protective effect is smaller, but on balance there does seem to be a slight protec- tive effect. The risk of neck injury does not seem to be reduced by bicycle helmets. There are only four estimates of effect, but they all indicate an increased risk of injury. When the risk of injury to head, face or neck is viewed as a whole, bicycle helmets do provide a small protective effect. This effect is evident only in older studies. New studies, summarised by a random-effects model of analysis, indicate no net protective effect. So, *** "viewed as a whole, bicycle helmets do provide a small protective effect" *** your meta analyses buddies say And Jedediah wrote... Jedediah Mackenzie Weeks Andrew, have you seen the Walker study? (http://www.sciencedirect.com/science/article/pii/S0001457506001540) Yesterday at 2:34pm · Unlike · 2 Andrew Timleck @jedediah...neat piece... And crappy to see how (once again) women get the short end of being expected to be predictable drivers of bikes so motorists give them wider berth ( not to quibble but I would like to see more than the experimenter put on a wig to test it). The helmet thing and distance from road (if wearing motorists pass closer and distance from curb is inversely related to driver distance to cyclist if I'm reading correct) is also... Well, "bothersome"isn't real scientific ... But really suggests we have to rethink that stuff. The same kind of argument is made about ABS brakes in cars... Do they contribute to *more* risk not more safety in the end as drivers push the limits more. Good food for thought J. thanks for sharing it. So I will listen and acknowledge alternative outcomes. But the first article seals the deal... On the whole they reduce injury. And it wasn't my article it was someone else who brought it forward after my assertion. Sorry it was so much work to find. And, as before, good luck with your fight. I'm done here. Regards all.


 @baltobikeboi  @Wash_cycle Went to the bikemore fb page. Couldn't find any evidence that bike helmet laws are a proven method of reducing public harm. And I think WABA does a good job of noting that the amount that a helmet law will reduce cycling is an unknown with a wide error band. They don't misrepresent anything - and they give readers references to look it up for themselves. 

Switch to our mobile site