An interesting article to read. In simple terms however, in order to qualify for helmet exemption, the security cell and seat belts must be such that the head can not make contact with the road in a roll over.

Why the same rule does not apply to a 4 wheeled vehicle I do not know. Some sports cars from major manufacturers are fitted with reinforced windscreen pillars and roll over hoops in the bodywork behind the seats etc. but it does not seem to be obligatory.

Peter

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