There is probably more risk when wearing a helmet than when not. In the event of hitting something at anything much more than 30 - the additional weight of the helmet is more likely to break your neck. This is why HANS or R3 was invented, it limits the neck extension in the event of s crash. its not the same as a bike where the whole body is free to move, in the car if you wear a seatbelt and a helmet the risk just moves somewhere else. I remember reading that a car with a spike in the centre of the steering wheel is safer than an airbag because it makes you drive very carefully!
