Why did the injury rate triple after the helmet law?

Abstract

The injury rate has tripled since the helmet law.
By increasing the risk of accidents, helmets have made cycling more dangerous.
Wearing a helmet can make us feel safer. However feeling safe is different than being safe.

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A recent study reveals a steady increase in cycling injuries in New South Wales (NSW), Australia, after the helmet law. Between 1991 and 2000, cycling injuries increased sharply.

cycling_injuries
A 1996 cycling survey in Sydney revealed that cycling counts were 48% below 1991. According to the census, cycling in Sydney further decreased between 1996 and 2001. sydney_cycling_counts After adjusting for the number of injuries per number of cyclist, the injury rate is shown below:

cycling_injury_rate
A decade after the helmet law, the injury rate tripled, indicating a large increase in accidents.

Why did the injury rate triple?

How can the widespread wearing of a device that protects the head result in almost a 3 time increase in the risk of head injury? There are several reasons for this unexpected result.

Safety in numbers

There is a well-known phenomenon called safety in numbers. Research published in the Injury Prevention journal concluded:

“the behavior of motorists controls the likelihood of collisions with people walking and bicycling. It appears that motorists adjust their behavior in the presence of people walking and bicycling … A motorist is less likely to collide with a person walking and bicycling if more people walk or bicycle. Policies that increase the numbers of people walking and bicycling appear to be an effective route to improving the safety of people walking and bicycling.”

safety_in_numbers_6A key factor for cycling safety is the number of cyclists. This is “safety in numbers”. The fewer cyclists, the more dangerous cycling becomes.

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The “safety in numbers” effect has been measured. The 48% decline in cycling observed corresponds to an increase in risk by 48%.

Risk Compensation

A false sense of safety can induce people to take more risks, leading to more accidents and more injuries. This is risk compensation, a well-known safety factor:

“the law of unintended consequences is extraordinarily applicable when talking about safety innovations. Sometimes things intended to make us safer may not make any improvement at all to our overall safety”

risk-compensation

Risk compensation is the tendency to take more risks when wearing safety equipment.
Lured by a false sense of safety, helmeted cyclists take more risks and have more accidents.
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Wearing a helmet can induce cyclists to take more risks, as reported in the New York Times:

the rate of head injuries per active cyclist has increased 51 percent just as bicycle helmets have become widespread. …

the increased use of bike helmets may have had an unintended consequence: riders may feel an inflated sense of security and take more risks. …

The helmet he was wearing did not protect his neck; he was paralyzed from the neck down. …

”It didn’t cross my mind that this could happen,” said Philip, now 17.
”I definitely felt safe. I wouldn’t do something like that without a helmet.” ”

Safety experts recognise the role of risk compensation. From the New York Times article:

”People tend to engage in risky behavior when they are protected,” he said. ”It’s a ubiquitous human trait.”

Even cyclists who discount the daredevil effect admit that they may ride faster on more dangerous streets when they are wearing their helmets.

1989 study found that helmet wearers were 7 times more likely to have accidents.

Risk compensation also affects motorists who tend to be less careful around helmeted cyclists. As reported in a study published by the University of Bath in the UK:

“Bicyclists who wear protective helmets are more likely to be struck by passing vehicles”

Both the behaviour of helmeted cyclists and surrounding motorists increase the risk of accidents.

Cycling injuries have kept rising throughout the 1990’s. This coincided with helmet promotion campaigns exaggerating the benefits of helmets. This may have given cyclists a false sense of safety.

Degrading the bicycle helmet standard

Before the helmet law, Australia’s bicycle helmet standard required hard shells. Government research warned of deficiencies in the standard, as helmets can increase brain injury.

The research recommended improvement to the standard. Instead, the government degraded Australia’s helmet standard to accommodate ”soft-shell helmets”. Soft-shell helmets are more comfortable and facilitate compulsory helmet wearing. However they provide little protection and can cause brain injury.

hard-shell-vs-soft-shell-helmet By degrading the helmet standard, the government legitimized a weaker helmet. Calling a polystyrene hat a “helmet” doesn’t give it protective abilities. Still, it can fool people into believing that it provides more protection than it does. This is likely to have contributed to the increase in head injuries after the helmet law.

Discouraging the safer cyclists

Following the helmet law, many cyclists who used a bicycle for transport gave up cycling. Transport cyclists have fewer injuries than sport cyclists. The increase in injuries after the helmet law can in part be explained by a reduction in transport cycling. However, the reduction in transport cycling cannot have quadrupled the injury rate.

Summary

The injury rate has tripled since the helmet law. This is most likely due to:
  1. safety in numbers: the risk of accidents increased as there were fewer cyclists.
  2. risk compensation: helmeted cyclists lured into a false sense of safety, taking more risks.
  3. Degrading the helmet standard to include polystyrene “helmets” that provide little protection.
  4. The safer cyclists stopped cycling.

But wait, the study claims the helmet law was a success!

Despite the large increase in head injuries, the study claims:

“the benefit of MHL to lowering head injuries”

How can the study make such a claim?

  1. It ignored the decrease in cycling measured by cycling surveys.
  2. It ignored the increase in injuries.

This study is like doing a cost benefit analysis while ignoring the costs and exaggerating the benefits.

This “study” was commissioned by a government struggling to justify its policy. Bureaucrats quote this study claiming:

“A recent study from the University of New South Wales showed that the initial benefits of the mandatory helmet laws have been maintained over time.”

What?

Do they think we are complete fools?

This study did not fool a reporter:

As the fallout from Australia’s failed bike sharing schemes continues, it seems we haven’t seen the last of government-funded research showing that helmet laws are great actually, thanks very much. …

The authors, Olivier, Walter and Grzebieta, previously published a paper in 2011 claiming to “end the debate about the effectiveness of cycle helmet legislation”, but which was severely criticised by fellow boffins

the government of NSW has commissioned research which (surprise!) finds the effect of their helmet law is massive and sustained, ignoring the uncomfortable fact that helmet wearing rates have actually fallen back significantly without any accompanying jump in head injuries. The authors …  include all types of minor flesh wounds, bruising etc. which you would certainly hope would be prevented by helmet use, rather than looking at a reduction of critical injury / death which is what public health policy should be worrying about, when the alternative is serious sedentary disease. It’s generated some nice headlines and superficial reinforcement for the helmet law (which is probably what the government were really trying to commission).

Such a “study” helps bureaucrats deny they made a mistake.

How does that serve the public?

The fundamental role of science is to serve the truth. It is NOT to serve the interests of the state.

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