It's contentious. It's suggested they may prevent certain injuries (fracture) but exacerbate others (rotational/shearing). So wearing a helmet may prevent a l

It's contentious. It's suggested they may prevent certain injuries (fracture) but exacerbate others (rotational/shearing). So wearing a helmet may prevent a large number of lesser injuries at the cost of causing a smaller number of more permanently damaging ones (although this a problem people are working on) http://en.wikipedia.org/wiki/Bicycle_helmet http://en.wikipedia.org/wiki/Bicycle_helmet http://www.abc.net.au/news/stories/2010/08/17/2985631.htm http://www.abc.net.au/news/stories/2010/08/17/2985631.htm http://members.pcug.org.au/~psvansch/crag/h-i-mech.htm http://members.pcug.org.au/~psvansch/crag/h-i-mech.htm