Category Archives: Myths

The myth that cycling is dangerous

You’ve heard it again and again:

“Cycling is dangerous”

When we keep hearing the same statement again and again, we end up believing it. This is a well-known manipulation technique, mentioned by Daniel Kanheman in his acclaimed book “Thinking fast and slow“:

“A reliable way to make people believe in falsehoods is frequent repetition, because familiarity is not easily distinguished from truth. Authoritarian institutions and marketers have always known this fact.”

How dangerous is cycling?

Not as dangerous as it has been portrayed. According to this assessment and this summary, cycling is less dangerous that walking for the same distance traveled.

In other words, cycling to the shops is less dangerous than walking to the shops.

Statistically, one can expect a severe head injury from cycling once every 8,000 years of average cycling.
Wardlaw M. British Medical Journal 2000;321(7276):1582 (23 December), doi:10.1136/bmj.321.7276.1582

What type of cycling might be dangerous?

Sweeping statements such as “cycling is dangerous fail to distinguish between very different types of cycling.

downhill-mountain-bike-small-3cycling downhilll

Sports cycling can be dangerous

Yet cycling as a mode of transport is safe.

lady cyclingThis is less dangerous than walking

bike_share_London This is even safer

With its low speed and upright position, bike share is safe. In London, after 7 million trips, there were no fatalities and only 9 injuries requiring hospitalisation. The serious injury rate is 3 times lower than for all cyclists.

But they keep telling me that all cycling is dangerous!

The myth that all cycling is dangerous comes from years of helmet promotion campaigns. Scaremongering tactics manipulate our fears to push helmets.

How do you promote helmets for a safe activity? Make it look more dangerous than it really is.

This is eloquently illustrated in this report:

“our politicians and transport bureaucrats feel compelled to constantly remind us of how dangerous cycling is …

“Don’t think that little ride to the shops warrants wearing [a helmet]? Well I’ve got news for you. Even on a short ride you could have a big fall and you could suffer a major brain injury.”

Misconception 1: Cycling is dangerous. … Melbourne newspaper The Age quoted an emergency physician who opined that riding a bicycle on Melbourne’s roads was “verging on suicide” – an almost hysterical assessment of the risk. ….

The reality is that riding a bicycle is a safe activity. The following table shows Australian government data on the relative injury risk of a number of sporting and recreational activities.  …

Unfortunately, despite the evidence, governments continue to portray cycling as unusually dangerous”

The claim made in the fear mongering propaganda quoted above is particularly misleading, considering that cycling to the shops is safer than walking to the shops. Even though cycling is less dangerous than many comparable activities, it is portrayed as being particularly dangerous.

A funny parody of this ad highlights how cycling is misrepresented as being far more dangerous than it really is.

Not every country suffers from fear mongering tactics from their government. In the UK, the transport minister admits that:

(cycling is) a “safe activity” … safer than walking

In Canada, the hysteria about cycling being “dangerous” is being challenged in the media:

“bicycling had the lowest “burden” of deaths and head injuries of the three transportation modes …

There were 14 deaths per 100 million trips for bicycling, 15 for walking and 10 for driving – remarkably similar. …

Are these risks high? One way to think about this is the number of trips for one death to happen: one car occupant dies every 10 million trips and one pedestrian or cyclist dies every seven million trips. ….

Both walking and bicycling are active modes of travel. The physical activity they entail reduces the risk of developing many chronic diseases, including heart disease, diabetes, certain cancers, and dementia. Many studies have compared these benefits to the injury risks. All have found that the benefits greatly outweigh the risks. The benefits of walking and cycling (lower risk of death from chronic diseases) are 10 to 100 times higher than the risk of death from injuries

US data reports:

“Research studies and data clearly show that, in the current environment, cycling benefits greatly outweigh its tiny risks. We know of no study that contradict this fact.

Contrary to common belief, cycling is safer than many other activities.

Cycling is over three times safer, per mile, than walking.

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The fallacy of the cracked helmet

We tend to look at a cracked helmet and assume it is “proof” it saved a life.
Actually, a cracked helmet has failed to work as intended:

“The next time you see a broken helmet, suspend belief and do the most basic check – disregard the breakages and look to see if what’s left of the styrofoam has compressed. If it hasn’t  you can be reasonably sure that it hasn’t saved anyone’s life.“

Polystyrene-based helmets protect by absorbing the energy of the impact through compressing the polystyrene. In a serious accident, polystyrene helmets tend to break into pieces. If the polystyrene has broken into pieces but not compressed, it has failed to work as intended.

soft-shell-helmet A bicycle helmet is a piece of polystyrene covered by a thin layer of plastic.
Notice how the helmet has cracked, but the polystyrene did not compress.
This indicates the helmet failed to absorb the energy of the impact.

We have a tendency to attribute causality from the timing of events. If we notice a cracked helmet and we do not have a head injury, we tend to attribute the lack of head injury to the helmet. Yet, cyclists fall with and without helmets, and rarely get a serious head injury in either case.

Protection is good, except when it increases the risk of accident

Helmets can have unexpected side-effects. One surprising observation has been an increased risk of accidents. In Australia, cycling injuries tripled after the helmet law:

cycling_inury_rate_following_helmet_law_2

 In Australia, cycling injuries tripled after the helmet law.
Many of those extra injuries would have been “cracked helmet” scenarios.

How can the widespread wearing of helmets increase the risk of injuries? There is a well-known safety phenomenon called “risk compensation“. As we feel safer, we tend to take more  risks. More risks means more accidents.

Sometimes our intuition can be wrong

It is easy to forget that bicycle helmets are only designed to protect in minor impacts:

“In cases of high impact, such as most crashes that involve a motor vehicle, the initial forces absorbed by a cycle helmet before breaking are only a small part of the total force and the protection provided by a helmet is likely to be minimal in this context. In cases where serious injury is likely, the impact energy potentials are commonly of a level that would overwhelm even Grand Prix motor racing helmets. Cycle helmets provide best protection in situations involving simple, low-speed falls with no other party involved. They are unlikely to offer adequate protection in life-threatening situations.“

Dr Carwyn Hooper from St George’s University in London reports:

“Looking at evidence, it does not matter if people are wearing a helmet or not, any serious accident on a bike is likely to kill them”

Helmets increase the volume of the head, thus the chance of the head hitting the ground in an accident. Helmets also increase the risk of neck injuries, and can aggravate brain injuries. There is no guarantee that a fall with a helmet will result in less severe head, neck or brain injuries.

It is natural to assume a helmet saved us. But that doesn’t mean it is true. We don’t know what would have happened without it. Cyclists, with and without helmets, get hit by cars; the survival rates are identical. Most bicycle accidents do not result in serious head injuries, with or without helmets. We tend to overlook this, and attribute a lack of head injury to the helmet:

“see the double-standard of finding it entirely logical when helmeted cyclists who survive collisions report that wearing a helmet saved their life. It is a powerful emotional argument, but logically, statistically, and scientifically, it is erroneous for the same reasons it would be erroneous to say that not wearing a helmet saved Gene Hackman’s life. If a cyclist wears a helmet and they emerge from a collision alive, that implies correlation, not causation.”

Helmets can be deceptive

Cycling is a safe activity. Cyclists can expect a severe head injury once every 8,000 years of average cycling.

Wearing a helmet can increase the risk of accident. Wearing a device that increases the risk of accidents may not be the most effective way to enhance safety. It is ironic that a cracked helmet is hailed as “proof” it saved a life, while the accident may not have happened without it.

It is easy to be mislead, especially after a traumatic experience. It is important to be realistic about helmets capabilities, and to base that assessment on facts. Overestimating their protection can be dangerous. After a serious accident, it is too late to discover that bicycle helmets are not designed to protect in a serious impact.

Bicycle helmets can be insidious:

  1. At first, they seem to protect.
  2. They tend to increase the risk of accidents.
  3. They do not offer adequate protection in a serious accident.

Does the protection compensate for more accidents?

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The myth that bicycle helmets protect against brain injury

Abstract

Brain injury is caused by rotational acceleration.
Bicycle helmets are not designed to protect against it.
In some circumstances they can increase it, causing permanent disability.

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What surgeons say

This article reports from a surgeon who operates on cyclists:

“The ones with brain swelling, that’s diffuse axonal injury, and that’s bad news” …

the whole brain is shaken up, creating many little tears in its inner structure …

Such patients undergo personality change, can contract epilepsy and have difficulty controlling their anger. They might become unemployable. Depression is a common accompaniment to brain injury. Rosenfeld sees patients’ families shattered, too. “They’re never the same. It often leads to marriage disharmony and family breakdown.” …

Rosenfeld’s opinion is candid.  “I don’t know if [helmets] do much to protect the inner part of the brain,”

A neurosurgeon from the UK admits:

“I see lots of people in bike accidents and these flimsy little helmets don’t help.”

According to another Australian surgeon who operates on cyclists:

“The best evidence is that [a helmet] doesn’t make any difference to serious head injury when riding a bicycle …

initial research used to back the mandatory laws was “deeply flawed and criticised”. Some newer findings, he said, showed that these laws could increase the chance of serious injury. “

Sport cyclists are having doubts

Helmets are part of the sport cyclist uniform. Yet fatalities have doubled since mandatory helmets:

The helmet rule for professional cyclists was brought by the UCI in 2003 following the death of Andrei Kivlev during the Paris-Nice race.

Since then deaths of professional cyclists while racing have doubled, so where is the protection that helmets are supposed to give a rider?

Sport cyclists are having doubts, as reflected in a recent edition of Bicycling Magazine:

new research is finding that concussions could be as dangerous as splitting open your skull. And that brain bucket you own? It was never designed to prevent concussions.

Distinguishing between focal brain injury and diffuse brain injury

What’s going on? Why do people believe that bicycle helmets protect against brain injury while surgeons say they don’t? Much of the confusion comes from a lack of distinction between focal brain injury and diffuse brain injury.

An old popular belief is that brain injury is caused by a direct hit the head, like a head hitting a wall, causing linear acceleration. This is focal brain injury. Bicycle helmets are designed to reduce focal injury. The polystyrene reduces linear acceleration by compressing on impact.

Scientific research done in the 1970’s has revealed that the main cause of severe brain injury is not focal injury but diffuse axonal injury:

“The experiments gave special attention to direct comparison of the contributions of linear and angular acceleration because the widely accepted Head Injury Criterion for head injury is based on measurements of the former – see below. The essential role of angular acceleration in producing cerebral concussion was shown, the threshold being estimated as 2000-3000 rad/sec². Translation was also responsible for brain injuries, albeit only focal, and did not produce concussion.  …

Along with the support which research has provided for the new theory, it has discredited the notions of coup and contre-coup and of linear acceleration of the brain being a major factor in injury to it.”

Diffuse axonal injury, also called rotational injury, is caused by angular acceleration, for example when the head rotates quickly. The skull may be intact, but there can be severe internal brain damage. This is what the surgeon Dr.  Rosenfield was describing in the article mentioned above.

Some people believe helmets protect against brain injury. Not only is this not true, but the opposite is more likely to be the case:

“Protecting the brain from injury that results in death or chronic disablement provides the main motivation for wearing helmets. Their design has been driven by the development of synthetic polystyrene foams which can reduce the linear acceleration resulting from direct impact to the head, but scientific research shows that angular acceleration from oblique impulse is a more important cause of brain injury. Helmets are not tested for capacity to reduce it and, as Australian research first showed, they may increase it.

Even though helmets do not protect against brain injury, fear of chronic disability has been used to promote them. This has lead to an exaggerated opinion of the protection provided by helmets. A false sense of safety can lead to increase risk taking, as reported in the New York Times:

“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. …

”I definitely felt safe. I wouldn’t do something like that without a helmet.” 

Research on bicycle helmets

Soft-shell helmets, the most common type of bicycle helmet, are helmets without a hard shell. They have a thin layer of plastic on top, less than 1 mm.

soft-shell-helmet A soft-shell helmet is a piece of polystyrene covered by a layer of plastic less than 1mm thick.

In 1987, an Australian government agency released research that highlighted deficiencies with bicycle helmets:

The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage. It is quite apparent that the liner material in children’s bicycle helmets is far too stiff …

rotational accelerations were found to be 30% higher than those found in similar tests using a full face polymer motorcycle helmet. More work needs to be done in this area as there would seem to be a deficiency in rotational acceleration attenuation that may be the result of insufficient shell stiffness

Helmets can increase brain injury, according to research done in Sweden:

“The non-shell helmet did in all trials grab the asphalt surface, which rotated the head together with
the helmet. The consequences were in addition to the rotating of the head, a heavily bent and compressed neck, transmitted on through the whole test dummy body after the impact.  …

This gives an average angular acceleration of 20800 rad/s² for rotating the head from 0 to 0.26 rad during the 5 ms. Löwenhielm proposes 4500 rad/s² to be the maximum angular acceleration that can be tolerated for a limited time period”

Soft-shell helmets amplified rotational acceleration to four times higher than the tolerable maximum.

On impact, the larger head volume amplifies rotational acceleration. 3cm increase in helmet circumference increases rotational acceleration by 150%:

“the 3000rad/s² to 8500rad/s² measured during abrasive and projection oblique tests with size 54cm (E) helmeted headforms. However, for the most severe cases using a size 57cm (J) headform, rotational acceleration was typically greater than 10,000rad/s² and increased to levels of 20,000rad/s², a level at which a 35% – 50% risk of serious AIS3+ injuries is anticipated.”

The difference between a helmeted and non-helmeted head is about 20cm.

The mechanics of bicycle helmets

Helmets increase the volume of the head.  In the event of an accident, this increases the risk of the head hitting the road. Post-crash studies found that most helmets show impacts to the side, where a bare head is protected by the shoulders.

helmet-head-size-2

Helmets increase volume of the head, doubling  chance of the head hitting the road in an accident.
The larger volume amplifies rotational acceleration, the main cause of brain injury.
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Is this just a theory?

Unfortunately it doesn’t seem like it.

doctor from New Zealand reports:

“cycle helmets were turning what would have been focal head injuries, perhaps with an associated skull fracture, into much more debilitating global head injuries”

In Canada, the length of stay in hospital increased increased following helmet laws, from 4.3 days to 6.9 days. The number of serious head injury admissions increased by 46%.

Helmeted riders are more than twice as likely to hit their head in an accident, with more impacts to the sides. A 1988 study reports that helmeted riders hit their heads seven times more often than un-helmeted riders.

In the US, a strong rise in helmet wearing was followed by an increase in head injuries:

“Bicycle helmets might not protect cyclists much at all.  And, in fact, in some cases, they might actually be more dangerous than going lidless. …

head injuries had increased even though the use of helmets had skyrocketed throughout the 1990s.  The risk of injury per cyclist had gone up by 51%. …

We don’t know what’s going on,” said one political appointee who should know.  Well, I’ll offer my idea.  People accepted the idea that helmets work, and then created studies to “prove” that they do. “

It is easy to take things for granted, and to assume that a device labeled a “helmet” can only protect, and cannot make things worse.

What about the studies that claim that helmets protect against 80% of brain injuries?

There have been many “studies” claiming that helmets protect against brain injuries. The most famous one was done by helmet lobbyists and funded by the helmet industry. This “study” had methodological errors. It was the basis for a US government claim that helmets reduce 85% of head injuries. The US government has since dropped this claim.

Many studies assume that helmets are effective and attempt to “prove” it. Such studies jump to a predetermined conclusion, with a disturbing lack of scientific discipline. Often the claims are contradicted by the study’s own data.

Governments who enacted helmet law have funded policy-driven studies defending their policy. Such “studies” use biased statistics, resulting misleading claims. Bill Curnow, a scientist from the CSIRO, wrote as a conclusion of a scientific article:

“Compulsion to wear a bicycle helmet is detrimental to public health in Australia but, to maintain the status quo, authorities have obfuscated evidence that shows this.”

In 2011, the New South Wales government funded a study trying to deny that helmets can aggravate brain injury. This risk exists for soft-shell helmets at high speed. The “study” set up unrealistic conditions at low speed, then magically generalized the results. This is deceitful as the unrealistic conditions are not representative of real life accidents.

The dilemma: minor skull injuries vs brain injury

Bicycle helmets are designed to protect cyclists if they fall on top of their heads at speeds below 20 km/h. They mitigate against minor skull injuries like bruises and lacerations. They are not tested for side impacts.

Is it worth to increase the risk of brain injury to mitigate minor skull injuries? An Australian cyclist challenged a helmet fine as helmets can increase brain injury. After reviewing evidence in a court of law, District Court Judge Roy Ellis concluded:

“”Having read all the material, I think I would fall down on your side of the ledger …

I frankly don’t think there is anything advantageous and there may well be a disadvantage in situations to have a helmet  and it seems to me that it’s one of those areas where it ought to be a matter of choice.”

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My helmet saved my life!

Abstract

After the helmet law, many cyclists insisted that their helmets had saved them.
Yet cycling injuries tripled.
Why? Because helmets increase the risk of accidents.
 

What the data tells us

Here are some stats on cycling death & serious injury for children in NSW, before and after the helmet law. Two years after the introduction of the helmet law, death and serious injuries decreased by 32%. Hooray! This proves that helmet saved lives! That is what many government commissioned studies have claimed.

Can this 32% decrease be fully attributed to helmets though? What if it was due to something else? Like what? Like a decrease in the number of cyclists. After the helmet law, the number of child cyclists in NSW decreased by 44%. The decrease in death & serious injuries was less than the reduction in cycling.

The helmet law was introduced at the same time as other road safety measures, like a crackdown on speeding and drink driving. This would have benefited cyclists and pedestrians. Pedestrians death and serious injuries decreased by 23% during this period.

The risk of death and serious injuries for cyclists, adjusted for the lower number of cyclists, increased by 21%.  For pedestrians it decreased by 21%.

It seems that the helmet law has made cycling more dangerous.

Hmm …..

Where are the cyclists saved by their helmets?  They cannot be found in the injury data. Many people claim a helmet saved their life. Yet the risk of death and serious injury has increased.

Why have helmets failed to reduce injuries?

One possible explanation is that the risk of accident tripled.

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 tend to have more accidents.
blank
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.” ”

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.

 

There is a well-known phenomenon called safety in numbers. According to empirical data, reducing cycling by 44% increases the risk of accidents by 41%. 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_6

A key factor for cycling safety is the number of cyclists.  This is “safety in numbers”.
With fewer cyclists, cycling becomes more dangerous.
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What protection do helmets provide?

Despite the increase in accidents, helmets should have saved these people. Helmets saved some of them, as the 55% increase in the risk of death & serious injury is lower than the 93% increase in accidents. Yet overall the risk of death & serious injury increased.

Unfortunately polystyrene based helmets are not designed to protect in a serious accident:

“In cases of high impact, such as most crashes that involve a motor vehicle, the initial forces absorbed by a cycle helmet before breaking are only a small part of the total force and the protection provided by a helmet is likely to be minimal in this context. In cases where serious injury is likely, the impact energy potentials are commonly of a level that would overwhelm even Grand Prix motor racing helmets. Cycle helmets provide best protection in situations involving simple, low-speed falls with no other party involved. They are unlikely to offer adequate protection in life-threatening situations.

soft-shell-helmet

A soft-shell helmet is a piece of polystyrene covered by a layer of plastic less than 1mm thick.
It can protect in a minor accident.  However, it is not designed to protect in a serious accident.

 

Helmets make little difference in a serious accident, as Dr Hooper reports:

“Looking at evidence, it does not matter if people are wearing a helmet or not, any serious accident on a bike is likely to kill them,”

Suspending belief

On one hand, we have plenty of anecdotes from people who claim that a helmet saved their lives.
On the other hand, we have an increased risk of death and serious injury after the helmet law.
Both cannot be true at the same time.
Perhaps it would be more accurate to say that some people BELIEVE that a helmet saved them:

“The next time you see a broken helmet, suspend belief and do the most basic check – disregard the breakages and look to see if what’s left of the styrofoam has compressed. If it hasn’t, you can be reasonably sure that it hasn’t saved anyone’s life.

A helmet protects by absorbing the energy of the impact through compressing the polystyrene layer. If the polystyrene has not compressed, but has broken into pieces instead, it has failed. It may have prevented bruises & lacerations, but it didn’t do much to reduce the energy of the impact.

One can expect a severe head injury from cycling once every 8,000 years of average cycling.

It is natural to assume a helmet saved us. But that doesn’t mean it is true. We don’t know what would have happened without it. Cyclists, with and without helmets, get hit by cars; the survival rates are identical. Most bicycle accidents do not result in serious head injuries, with or without helmets. We tend to overlook this, and attribute a lack of head injury to the helmet:

“see the double-standard of finding it entirely logical when helmeted cyclists who survive collisions report that wearing a helmet saved their life. It is a powerful emotional argument, but logically, statistically, and scientifically, it is erroneous for the same reasons it would be erroneous to say that not wearing a helmet saved Gene Hackman’s life. If a cyclist wears a helmet and they emerge from a collision alive, that implies correlation, not causation.”

It is important to be realistic about helmets capabilities, and to base that assessment on facts rather than personal experiences, however traumatic they may be.

After being asked

“Can your helmet save your life?”,

a helmet manufacturer salesperson shrugged and laughed uncomfortably, before responding:

“Can it?” “Well, not save your life, no.”

This doesn’t mean that it is not possible that a helmet saved a cyclist life. It might have in some cases. However, few people consider that the lack of a helmet tends to make them ride more cautiously, and have fewer accidents. If they weren’t wearing a helmet, they may not have had a crash in which their life needed saving in the first place.

In many other instances, a helmet failed to save cyclists. Overall the risk of death & serious injury increased after the helmet law.

Before claiming that a helmet saved your life, ask:

  • How do I know what would have happen without a helmet?
  • Would I have ridden more cautiously without a helmet?
  • Is it reasonable to rely on a piece of polystyrene to save my life in a serious accident?
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Do helmets really protect racing cyclists?

Most sport cyclists wear a helmet as it is “obvious” it protects.  Does it?

Since mandatory helmets, deaths of professional cyclists while racing have doubled:

“The helmet rule for professional cyclists was brought by the UCI in 2003 following the death of Andrei Kivlev during the Paris-Nice race.

Since then deaths of professional cyclists while racing have doubled, so where is the protection that helmets are supposed to give a rider?

It seems to me that there is too much emphasis on the part of manufacturers in designing something that looks cool rather than do what it is supposed to do, and that is protect a rider in the event he or she should hit their head.”

Dr Carwyn Hooper from St George’s University in London reports:

“Looking at evidence, it does not matter if people are wearing a helmet or not, any serious accident on a bike is likely to kill them,”

Polystyrene helmets are designed to mitigate falls below 20 km/h. Professional cyclists travel at speeds of 40 to 50 km/h, increasing to 80 km/h in downhill sections.

Why is it deemed essential that racing cyclists wear devices that are not designed to protect them? The Union Cycliste Internationale, the sport’s ruling body, first tried to impose helmets in 1991, but failed. It finally imposed them in 2003, using a tragic accident as an excuse. This opened up a new stream of sponsorship income for professional cycling.

Bicycle helmets:

  1. increase the risk of accidents
  2. increase the risk of neck injury
  3. increase the risk of brain injury

Does the protection compensates for these risks?

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Are bicycle helmets dangerous?

Abstract

Helmets protect against minor skull injuries like bruises and lacerations.

Helmets:

  1. increase the risk of accidents
  2. increase the risk of neck injury
  3. increase the risk of brain injury

It is not safe to assume that the protection outweighs the risks.

 

Some politicians claim “Helmets save lives“.

Is this true? CRAG has asked for evidence, but the government has been unable to provide any.

Even helmet salespeople do not make such claims. After being asked

Can your helmet save your life?“,

a helmet salesperson shrugged and laughed uncomfortably, before responding

Can it?” “Well, not save your life, no.

What is it that politicians know that helmet salespeople don’t?

What protection do helmets provide?

soft-shell-helmetA bicycle helmet is a piece of polystyrene covered by a layer of plastic less than 1mm thick.
It can protect in a minor accident.  However, it is not designed to protect in a serious accident.

Bicycle helmets are a piece of styrofoam designed to protect in minor impacts:

“In cases of high impact, such as most crashes that involve a motor vehicle, the initial forces absorbed by a cycle helmet before breaking are only a small part of the total force and the protection provided by a helmet is likely to be minimal in this context. In cases where serious injury is likely, the impact energy potentials are commonly of a level that would overwhelm even Grand Prix motor racing helmets. Cycle helmets provide best protection in situations involving simple, low-speed falls with no other party involved. They are unlikely to offer adequate protection in life-threatening situations.“

In serious accidents, they tend to disintegrate on impact, absorbing little energy. This crumbling is what many people mistake the helmet for as having saved their life:

“The next time you see a broken helmet, suspend belief and do the most basic check – disregard the breakages and look to see if what’s left of the styrofoam has compressed. If it hasn’t, you can be reasonably sure that it hasn’t saved anyone’s life.“

Dr Carwyn Hooper from St George’s University in London reports:

“Looking at evidence, it does not matter if people are wearing a helmet or not, any serious accident on a bike is likely to kill them,”

Bicycle helmets protect against bruises and minor lacerations.
Yet, cycling injuries tripled after Australia introduced a helmet law.

cycling_inury_rate_following_helmet_law_2
The rate of cycling injuries tripled after Australia introduced a helmet law.

How can the widespread wearing of helmets increase the risk of injuries?

Although helmets protect, they can also increase the risk of accidents.

Increase risk of accidents

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-compensationRisk compensation is the tendency to take more risks when wearing safety equipment.

Wearing a helmet can induce cyclists to take more risks. This can lead to permanent disability, 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”

Children are affected by risk compensation, as reported in Accident Analysis and Prevention :

“Results indicated that children went more quickly and behaved more recklessly when wearing safety gear than when not wearing gear, providing evidence of risk compensation.”

Helmets encourage people to ride faster, as reported by the Risk Analysis international journal:

“those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster

The severity of injuries is much higher at higher speeds.

Many people believe that helmets protect against brain injury. Do they?

What causes brain injury?

In 1960, people believed that brain injury was due to linear acceleration, from the head hitting a wall for example. This belief has shaped the design of bicycle helmets.

Since, scientific research has shown that the main cause of brain injury is diffuse injury, caused by the head turning quickly. The skull may be intact, but there can severe internal brain injury. This article reports from a surgeon who operates on cyclists:

” “The ones with brain swelling, that’s diffuse axonal injury, and that’s bad news” …

the whole brain is shaken up, creating many little tears in its inner structure …

Such patients undergo personality change, can contract epilepsy and have difficulty controlling their anger. They might become unemployable. Depression is a common accompaniment to brain injury. Rosenfeld sees patients’ families shattered, too. “They’re never the same. It often leads to marriage disharmony and family breakdown.” …

Rosenfeld’s opinion is candid. “I don’t know if [helmets] do much to protect the inner part of the brain,” “

Helmets can increase brain injury, according to this research:

“The non-shell helmet did in all trials grab the asphalt surface, which rotated the head together with
the helmet. The consequences were in addition to the rotating of the head, a heavily bent and compressed neck, transmitted on through the whole test dummy body after the impact.  …

This gives an average angular acceleration of 20800 rad/s² for rotating the head from 0 to 0.26 rad during the 5 ms. Löwenhielm proposes 4500 rad/s² to be the maximum angular acceleration that can be tolerated for a limited time period”

Helmets amplified rotational acceleration to four times higher than the tolerable maximum.

On impact, the larger head volume amplifies rotational acceleration. A 3cm increase in helmet circumference increases rotational acceleration by 150%:

“the 3000rad/s² to 8500rad/s² measured during abrasive and projection oblique tests with size 54cm (E) helmeted headforms. However, for the most severe cases using a size 57cm (J) headform, rotational acceleration was typically greater than 10,000rad/s² and increased to levels of 20,000rad/s², a level at which a 35% – 50% risk of serious AIS3+ injuries is anticipated.”

The difference between a helmeted and non-helmeted head is about 20cm.

Increase risk of the head hitting the road

In the event of an accident, helmets increase the risk of the head hitting the road.  Helmets increase the volume/size of contact area of the head. Helmeted riders are more than twice as likely to hit their head in an accident, with more impacts to the sides. Post-crash studies found that most helmets show impacts to the side,where a bare head is protected by the shoulders.

helmet-head-size-2

Helmets increase volume of the head, doubling chance of the head hitting the road in an accident;
The larger volume also amplifies rotational acceleration, the main cause of brain injury.
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A 1988 study reports that helmeted riders hit their heads seven times more often than un-helmeted riders.

Helmets are not suitable for children’s more deformable head

In 1987, the Federal Office of Road Safety published research on helmets. This research highlighted serious deficiencies with bicycle helmets:

The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage. It is quite apparent that the liner material in children’s bicycle helmets is far too stiff …

rotational accelerations were found to be 30% higher than those found in similar tests using a full face polymer motorcycle helmet. More work needs to be done in this area as there would seem to be a deficiency in rotational acceleration attenuation that may be the result of insufficient shell stiffness. 

child cycling 4

Bicycle helmets helmets are designed for adult heads. They are too stiff for children more deformable heads. Despite this, helmets are promoted as “protecting” children, without appropriate warnings.

Helmets are associated with more severe brain injuries

New Zealand doctor reports:

“cycle helmets were turning what would have been focal head injuries, perhaps with an associated skullfracture, into much more debilitating global head injuries”

In Canada, the length of stay in hospital increased increased following helmet laws, from 4.3 days to 6.9 days. The number of serious head injury admissions increased by 46%.

Do helmets provide a net safety benefit?

Bicycle helmets are a safety trade-off. They protect the skull against bruises and lacerations. But they increase the risk of accidents and can increase brain injury.

Evidence provided in court suggests that helmets provide limited protection.:

“So in at least one case now, a High Court has decided that the balance of probability was, in the matter before the Court, that a cycle helmet would not have prevented the injuries sustained when the accident involved simply falling from a cycle onto a flat surface, with barely any forward momentum. …

the QC … repeatedly tried to persuade the neurosurgeons … to state that one must be more safe wearing a helmet than would be the case if one were not. All three refused to do so, claiming that they had seen severe brain damage and fatal injury both with and without cycle helmets

recent meta-analysis of helmets effectiveness reports reports no net beneficial effect. They do not protect against facial injuries, and increase neck injuries.

The belief that helmets can only improve safety may be a myth:

“Bicycle helmets might not protect cyclists much at all.  And, in fact, in some cases, they might actually be more dangerous than going lidless. …

head injuries had increased even though the use of helmets had skyrocketed throughout the 1990s.  The risk of injury per cyclist had gone up by 51%. …

We don’t know what’s going on,” said one political appointee who should know.  Well, I’ll offer my idea.  People accepted the idea that helmets work, and then created studies to “prove” that they do. “

We do not know whether helmets provide a net safety benefit. We do know that injuries have increased after a helmet law was imposed in Australia. The risk of death & serious injury increased by 50% for child cyclists. 

The UK’s National Children’s Bureau provided a detailed review of cycling and helmets in 2005:

“The conclusion from the arguments outlined above is that the case for cycle helmets is far from, sound. The strong claims of injury reduction made by helmet proponents have not been borne out for fatalities (which this paper argues is the most methodologically sound test of effectiveness) in real-life settings with large populations. …

the benefits of helmets need further investigation before even a policy supporting promotion can be unequivocally supported. ….

The cycle helmet debate shows the dramatic power of real life events in shaping our understanding of causality. Tragedies happen; child cyclists are killed or left disabled for life; and we cannot let go of the belief that something 
could and should have been done to stop that particular event from happening – especially when that something is so simple as wearing a helmet. We find it hard to accept that the helmet may have made no difference. We find it harder to accept that encouraging or forcing children to wear helmets might also encourage them to ride in a more dangerous way and paradoxically to increase the risk that they will suffer an accident. And we find it much harder to accept that compulsory helmet use might put children off cycling altogether, leaving them less physically active, and – many years later – more likely to die of heart disease.Think of all the uncertainty behind that line of argument, compared with the seeming rock-solid conviction that a helmet could have saved that particular child’s life, at that particular time. And of course the fact that we are talking about children, who have a claim on our protection and who are still getting to grips with the world, makes it so much more difficult to accept the limitations on our ability to prevent them coming to harm. We cannot ignore the human suffering, pain and loss that lie behind the research and statistics. But our response to it demands reflection and perspective as well as sympathy and conviction.

Is it worth to increase the risk of brain injury to mitigate minor skull injuries? An Australian cyclist challenged a helmet fine as helmets can increase brain injury. After reviewing evidence in a court of law, NSW District Court Judge Roy Ellis concluded:

“”Having read all the material, I think I would fall down on your side of the ledger …

I frankly don’t think there is anything advantageous and there may well be a disadvantage in situations to have a helmet  and it seems to me that it’s one of those areas where it ought to be a matter of choice.

What about the studies that claim that helmets protect against 80% of head injuries?

There have been many “studies” claiming that helmets protect against brain injuries. The most famous one was done by helmet lobbyists and funded by the helmet industry. This “study” had methodological errors. It was the basis for a US government claim that helmets reduce 85% of head injuries. The US government has since dropped this claim.

Many studies assume that helmets are effective and attempt to “prove” it. Such studies jump to a predetermined conclusion, with a disturbing lack of scientific discipline. Often the claims are contradicted by the study’s own data.

Governments who enacted helmet law have funded policy-driven studies defending their policy. Such “studies” use biased statistics, resulting in misleading claims. Bill Curnow, a scientist from the CSIRO, wrote as a conclusion of a scientific article:

“Compulsion to wear a bicycle helmet is detrimental to public health in Australia but, to maintain the status quo, authorities have obfuscated evidence that shows this.”

In 2000, a government agency published a meta-analysis, that claimed to provide

overwhelming evidence in support of helmets for preventing head injury and fatal injury“.

This study was re-assessed by an independent researcher who concluded:

This paper … was influenced by publication bias and time-trend bias that was not controlled for. As a result, the analysis reported inflated estimates of the effects of bicycle helmets …

According to the new studies, no overall effect of bicycle helmets could be found when injuries to head, face or neck are considered as a whole

After attempts to justify its policy through misleading “studies”, and following CRAG submission to the Prime Minister in 2009, the federal government abandoned its compulsory helmets policy.

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