Two responses to D. Robinson’s 2005 study into helmet law efficacy perfectly summarise the helmet debate in Anglo-American countries. (I say Anglo-American because there is almost universal rejection of helmet laws in non-English speaking countries.)
The first, Arguments Against Helmet Legislation are Flawed, is typical of helmet & helmet law supporters. Numerous studies have shown that if involved in a crash, helmet wearing reduces the likelihood of serious head injury. Other studies have shown a correlation between helmet wearing through enforcement and a reduction in cycling injuries. Because helmets can be effective, they conclude that their use must be enforced and this enforcement has no negative effects.
The second, Determining True Effectiveness of Safety Measures, effectively captures our position that helmets are great but helmet laws are a disaster. Regardless how effective a particular safety measure might be in theory, failure to demonstrate any real benefits in whole populations over time must necessarily call into question its true effectiveness—particularly when compulsion is involved.
If helmet laws worked (a very different claim from whether or not helmets work), then we should have seen a reduction in cyclist head injuries compared with non-cyclist head injuries. Yet this is not the case.
If helmet laws worked, then we should have seen a reduction in the ratio of head to non-head injuries amongst cyclists (ie fewer head injuries for those that are in crashes). Again, this is not the case.
And if helmet laws were a difference maker to cyclist safety, then cycling with a helmet in Australia wouldn’t be over 10 times more dangerous than cycling without a helmet in Europe. But it is.