The argument I often hear for mandatory helmet laws is that they apparently "save lives". I am still yet to see any evidence of this. The evidence in my mind clearly shows that the greatest effect they had was to discourage cycling. The consequences are plain to see in the form of bulging stomachs and great swathes of public space given over without question to the storage and passage of motor vehicles.
Mandatory helmet laws are not a good example of evidence based policy.
One proven way of reducing road fatalities is to slow down traffic. This is of course disputed as the many letters to newspaper editors (no doubt from people caught speeding) show as they complain about revenue raising.
The British Medical Journal recently published the results of a study analysing traffic data from 1986 to 2006. It shows fairly clearly that reducing the speed limit on suburban roads to 20 mp/h (or 30 km/h) reduces fatalities. A pedestrian struck by a car travelling at 30 km/h has a very good chance of survival. Increase the speed to 50 km/h and that is reduced significantly. Increase it again to 60 km/h and the chances of a fatality start to increase at a greater rate than the speed increase.
You only have to recall the incredible whining and whinging that went on (and still does) after the introduction of 50 km/h default speed limits. Listen also to the incessant whining about 40 km/h zones in residential areas.
If this was really about safety, we would not have mandatory helmet laws but would instead have priority for cyclists and pedestrians and we would have 30 km/h speed limits in residential areas. The fact that we do not shows that these policies have nothing to do with safety but are more about pandering to spoiled motorists.