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He also cites an Australian study, which concludes risk of head injury per million hours travelled: Cyclist 0.41, Pedestrian 0.80, Motor vehicle occupant 0.46, Motorcyclist 7.66.

So if you want to be consistent you should update your comment to:

If you are cycling or driving wear a helmet.

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Okay, how's this :P

Cars have other safety equipment that make them unlike bicycles. These include airbags, seatbelts, crumple zones and the like.

If you are a driving, you should employ those safety devices when you do so.

Ok that leaves pedestrians, who have twice as many head injury's per km. Most likely due to being hit by cars - perhaps cars should have airbags on the outside too...

Volvo does have such a pedestrian airbag: https://www.youtube.com/watch?v=X2Aw4eZoijk

Apparently that model has scored the highest Euro NCAP crash test as of 2012 (the NCAP tests tests both damage to drive AND pedestrians).

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