ECF

Drivers overtaking cyclists passed an average of 8.5 cm closer to those wearing helmets. Source.

When Australia introduced mandatory cycle helmet law, bicycle usage dropped by 30%. Source.

The relationship between the number of cyclists and the number of casualties among cyclists involved in car accident is inverse. (The more cyclists, the less accidents among them). Source:  Hydén, C., A. Nilson & R. Risser (1998), WALCYNG. How to enhance WALking and CYcliNG instead of shorter car trips and make these modes safer. European Commission: WALCYNG