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 Helmet law repeal in Michigan: A four-year review
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DataDan
Advanced Member
542 Posts
[Mentor]


Central Coast, CA
USA

Yamaha

FJR1300

Posted - 10/12/2016 :  2:10 PM                       Like
In 2012, Michigan repealed its all-rider helmet law, allowing riders who meet these conditions to ride without a helmet:

  • Be at least 21 years old.
  • Have at least $20,000 in first-party medical benefits.
  • Have held a motorcycle endorsement for at least two years, or have passed an approved motorcycle safety course.

See previous discussion in this thread.

With the recent publication of Michigan Traffic Crash Facts 2015, it is possible to compare motorcycle crash data from four years after repeal to the four years preceding repeal (2008-2011). In this post I will summarize what I have compiled. Then, as time is available I may add some analysis and nerdish notes. If you have questions, please post them up.


  • In the four years since helmet law repeal (2012-2015), compared to the preceding four years, helmet use by Michigan motorcycle riders and passengers involved in crashes decreased from 98% to 74%.

  • Motorcyclist fatalities increased 9%, from an annual average of 116 to 126.

  • The number of motorcycles involved in crashes decreased 9% and the number of riders and passengers non-fatally injured decreased 11%.

  • From the above, it can be seen that while there were fewer crashes, crashing became more deadly. That can be measured as crash lethality, the percentage of motorcyclists involved in crashes who were killed. Lethality increased 12%, from 3.3% to 3.7%.

  • Lethality for helmeted riders decreased by 15%, from 3.2% to 2.7%. The helmeted riders who crashed after repeal were apparently involved in less severe crashes than the helmeted riders who crashed before repeal.

  • The number of motorcycles registered in the state dropped slightly, by 1.4%.

  • The crash rate--motorcycles involved in crashes per 1000 registrations--declined by 7.5%. The fatality rate per 10,000 registrations increased by 10%.

  • Estimates of annual motorcycle vehicle-miles traveled by state have not been consistently published, but a comparison can be made between 2009-10 and 2013-14, and Michigan motorcycle VMT increased 32%

  • In the years for which a VMT estimate is available, The crash rate per million VMT dropped 32% while fatalities per billion VMT fell 22%.

DataDan
Advanced Member
542 Posts
[Mentor]


Central Coast, CA
USA

Yamaha

FJR1300

Peer Review: 1

Posted - 10/12/2016 :  7:33 PM
I discovered something new today. I love it when that happens.

Enactment of a motorcycle helmet law (and repeal thereof) doesn't produce the change in fatalities one would expect, given the research showing helmet effectiveness at saving lives. (BTW, this is solid, widely accepted research, David Hough notwithstanding.) It has been observed over many years that repeal doesn't seem to increase deaths as much as predicted.

An obvious reason is that riders are aware of their added risk when riding unhelmeted and compensate by adjusting riding choices to reduce risk to a tolerable level. Deaths will still increase, but not as much as expected.

A reason I have hypothesized is that eliminating the helmet requirement brings into motorcycling riders who are generally at lower risk of crashing because they live in rural areas without traffic danger, because they are more conservative in their riding, or because they don't put on a lot of miles. Their arrival reduces annual population crash risk, which has a greater effect than the change in crash lethality.

Looking at the Michigan data today, I think I found another factor that limits the fatality increase after a helmet law is repealed. Note the following:

Lethality for helmeted riders decreased by 15%, from 3.2% to 2.7%. The helmeted riders who crashed after repeal were apparently involved in less severe crashes than the helmeted riders who crashed before repeal.

So for the 74% of post-repeal Michigan riders who wore helmets when they crashed, helmets became...more effective??? No. My guess is that the distribution of helmet benefits in the crashing population is uneven, and post-repeal helmet use is NOT random with respect to benefit.

Some motorcyclists are at greater risk of crashing in ways where a helmet won't be of much help. Suppose those riders prefer to ride helmetless when they have the option, while those who are less likely to experience such a violent crash continue to wear helmets. Greater helmet effectiveness will be found among the helmet wearers, which will be seen in lower lethality. And the crash lethality increase of the unhelmeted segment will less than expected, because their risk was already higher than average. Bottom line, post-repeal fatalities will be less than predicted.

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gymnast
Moderator
4267 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 10/13/2016 :  12:14 PM
Thanks for the data and the logical explanations Dan.
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wbrownell9
Male Junior Member
60 Posts


New Castle, DE
USA

BMW

R1200RT

Posted - 10/15/2016 :  8:53 AM
I might well be oversimplifying, but would it be fair in your opinion to say that those choosing to ride with helmets in the absence of a mandate to do so are also those who are temperamentally less likely to get into a situation where helmets would be helpful in mitigating injuries? This applies both to accidents due to riding over one's skill level (usually single-vehicle) and "avoidable" single- or multi-vehicle accidents (e.g. failure to maintain situational awareness for things like compromised traction or visibility, traffic developments, animals, etc.).

This is sort of like the argument about reducing crashes by enhancing visibility - are the data skewed because of selection bias? That is, do riders who actively try to be safe voluntarily enhance visibility (and wear helmets) whereas those that aren't as safety-focused don't exhibit those behaviors?

At the risk of putting words in your mouth (or electrons on the site ) I wouldn't be surprised if such conjecture can't be resolved with available data, but would be categorized as a confounding factor.
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gymnast
Moderator
4267 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 10/16/2016 :  2:04 PM
"those choosing to ride with helmets in the absence of a mandate to do so are also those who are temperamentally less likely to get into a situation where helmets would be helpful in mitigating injuries? This applies both to accidents due to riding over one's skill level (usually single-vehicle) and "avoidable" single- or multi-vehicle accidents (e.g. failure to maintain situational awareness for things like compromised traction or visibility, traffic developments, animals, etc.)."

If by "temperamentally" You mean a combination of factual knowledge, attitudes, and perhaps "quality of experience", you may be on to something, however measuring these qualities objectively is far more difficult than discussing them philosophically. I do, philosophically, agree with your premise.
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DataDan
Advanced Member
542 Posts
[Mentor]


Central Coast, CA
USA

Yamaha

FJR1300

Posted - 10/19/2016 :  4:34 PM
Helmet Law Repeal Effects by Age

Repeal of Michigan's motorcycle helmet law in 2012 had little effect on the ages of riders in crashes. But the lethality of crashing--the percentage of victims fatally injured--did change, and it affected age groups differently.

Here's a comparison of crash victims before and after repeal:

Pre-repeal crash involvement (2008-2011)

.age group ... victims ..... % .. fatalities ... lethality
..... < 21 ...... 1064 .... 7% .......... 24 ....... 2.26%
.... 21-24 ...... 1519 ... 10% .......... 46 ....... 3.03%
.... 25-34 ...... 2594 ... 17% .......... 80 ....... 3.08%
.... 35-44 ...... 2825 ... 19% .......... 83 ....... 2.94%
.... 45-54 ...... 3791 ... 25% ......... 140 ....... 3.69%
.... 55-64 ...... 2547 ... 17% .......... 67 ....... 2.63%
...... 65+ ....... 653 .... 4% .......... 22 ....... 3.37%

.... total ..... 12410 .. 100% ......... 392 ....... 3.05%


Post-repeal crash involvement (2012-2015)

.age group ... victims ..... % .. fatalities ... lethality
..... < 21 ....... 905 .... 7% .......... 16 ....... 1.77%
.... 21-24 ...... 1399 ... 10% .......... 49 ....... 3.50%
.... 25-34 ...... 2559 ... 19% ......... 104 ....... 4.06%
.... 35-44 ...... 2268 ... 17% .......... 84 ....... 3.70%
.... 45-54 ...... 3093 ... 23% ......... 107 ....... 3.46%
.... 55-64 ...... 2547 ... 19% ......... 101 ....... 3.97%
...... 65+ ....... 863 .... 6% .......... 41 ....... 4.75%

.... total ..... 11330 .. 100% ......... 437 ....... 3.66%


And this compares helmet use and helmeted and unhelmeted crash lethality by age:

Post-repeal helmet use and crash lethality (2012-2015)

.age group ... use .... helmeted .. unhelmeted ..... overall
..... < 21 ... 85% ....... 1.65% ....... 2.29% ....... 1.77%
.... 21-24 ... 82% ....... 2.96% ....... 5.35% ....... 3.50%
.... 25-34 ... 74% ....... 2.70% ....... 8.13% ....... 4.06%
.... 35-44 ... 66% ....... 2.55% ....... 6.58% ....... 3.70%
.... 45-54 ... 69% ....... 2.30% ....... 5.75% ....... 3.46%
.... 55-64 ... 74% ....... 3.04% ....... 6.56% ....... 3.97%
...... 65+ ... 82% ....... 3.86% ....... 7.33% ....... 4.75%

.... total ... 74% ....... 2.69% ....... 6.41% ....... 3.66%

Note that riders under 21 are required to wear helmets, so the fact that so many did crash unhelmeted (15%) demonstrates a problem of non-compliance when conditions aren't easily identified. There's no data on compliance with the insurance and training requirements for unhelmeted riding.

Note that helmet usage among riders 65+ was the same as the 21-24 group.

In a thread last year, I posted about the greater vulnerability of older riders in motorcycle crashes, based on California data. This data supports the same conclusion and shows, in addition, how valuable a helmet can be to those of us who are 65+.
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halsey
Male Senior Member
321 Posts


davison, mi
USA

Harley-Davidson

Road King

Posted - 12/30/2016 :  4:56 PM
So basically, ten people that need not die, did so because the law said they did not wear a helmet. I wonder if those folks who chose no helmet, were given the freedom of no helmet or life which would they choose? Dans Data proves the theory and Hurt study info that helmets save lives. Only a fool would do otherwise. What I did not see in the data, was neck injury totals and severities, broken jaws, smashed teeth and all else that goes with a face plant. Those are very vulnerable areas of the human anatomy when common sense is thrown out the window.
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