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| Table 1 shows the cause of ejection by helmet type in the 52 cases in which the cause was identified. The primary cause of helmet ejection is either "chin strap not fastened" or "slip-off" even though the chin strap was fastened (loosely or snugly). An unfastened chin strap, in particular, appears to cause helmet ejection even with minimum impact. This is surely why helmet ejection occurs at a certain percentage even at a low vehicle speed at the time of accident, as seen in Figure 8. The number of helmet ejections is high among half helmets and full face helmets, but for different reasons.
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In half helmets, "slip-off" numbered 16 cases, suggesting that the chin strap was not fastened securely. There were also a few cases in which the chin strap was not fastened at all. In full face helmets, on the other hand, helmet ejection was mostly caused by an unfastened chin strap. It is thus important to be aware that even a full face helmet, which covers the head extensively, can come off in an accident if the chin strap is not fastened. However, as seen in
Figure 8, the rate of helmet ejection does not rise with velocity over 90 km/h in motorcycle accidents. This would suggest that ejection can be prevented even in a high-speed accident if the proper type of helmet is chosen and worn securely.
In a moped or motorcycle accident, the head of the rider (or passenger) violently rebounds and rotates after crashing into a hard object. There is thus a considerable chance that the helmet may come off, as the collision may generate a strong force toward removing the helmet, or the motorcyclist's head may be twisted in a way that makes the chin strap slip out.
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Table 2 shows how the helmet was worn when it slipped off the head. The cause is mostly "chin strap fastened loosely". Wearing a helmet tilted back at an angle, choosing too large a helmet, or other factors that reduce the grip could also cause a helmet to slip off. Regarding half helmets, there were two cases in which helmets slipped off even though the riders were wearing them properly, suggesting that riders must be extra careful to fasten the chin strap of half helmets securely.
The above analysis clearly demonstrates the importance of buckling the chin strap firmly.
Why do some people fail to fasten the chin strap, or fasten it loosely? Here are some answers from those involved in accidents.
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Why was the chin strap not fastened or was fastened loosely?
Why not fastened?
- Can avoid no-helmet traffic tickets if a helmet is placed on the head-no need to fasten the chin strap.
- Fastening is troublesome.
- Uncomfortable if fastened.
- Quite safe even without fastening-I know the road well and don't speed.
- Since my helmet is full face, it is secure even without fastening the chin strap.
Why fastened loosely?
- Uncomfortable if fastened securely.
- To make it easy to put the helmet on and off.
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| Such excuses as ease of putting a helmet on and off and wearing comfort, rather than emphasis on safety, suggests bad habits and complacency. Such preferences are no excuse for not wearing a protective helmet.
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