Mandatory Helmet Laws
Australia is often used as an example of how mandatory helmet laws have decreased cycling participation.
There are increasing results of long term studies to support this.
"Bicycle helmets are compulsory in countries such as Australia and New Zealand, among others, but as the Guardian's Peter Walker explains this does not help save lives. Despite a series of helmet promotion campaigns in the UK, a growing amount of evidence suggests forcing people to wear protective headgear leads to greater risk-taking and can even put people off cycling altogether, exacerbating the crises in obesity and inactive living."