Bicycle helmet laws are motivated by a desire to improve safety. Yet when they have been implemented, the main result has been to reduce cycling. This imposes healths costs by reducing the health benefits of cycling. Are the benefits worth the costs? An Australian study concluded a helmet law may provide a small benefit under extreme assumptions.
A new study attempts to answer this question for Germany. It concludes that a bicycle helmet law is a waste of resource. This is despite optimistic assumptions favoring helmets, notably:
- It ignores the increased risk of accidents from risk compensation, a well-known safety factor.
- It assumes a helmet law only reduces cycling by 4%. This is inconsistent with evidence from countries with a helmet law, where cycling dropped by half.
- It assumes polystyrene helmets prevents fatalities. This is despite acknowledging in the discussion section that this is not true.
- It assumes a 100% compliance rate.
- It ignores enforcement costs.
- It assumes helmets reduce 50% of head injuries. The most recent research summary concludes helmets reduce 15% of head injuries, while increasing neck injuries.
- It ignores that helmets increase neck injuries.
Many of these assumptions are at odds with the available evidence.
The results from countries that have experimented with a bicycle helmet law are consistent:
- Cycling reduced by half
- The injury rate increased significantly
With such a track record, a bicycle helmet law has little to offer.
Even optimistic assumptions cannot make it viable.