The great disparity in risk of death and serious injury between motorised and sustainable traveller leads to very inequitable, and very unsustainable, access to the road network. Nearly half of the people killed and seriously injured on built-up roads (speed limits of 30 and 40mph) are pedestrians and cyclists, despite doing a tiny fraction of the mileage.

The reason for this disparity is very simple. A pedestrian struck at 20mph has a 95% chance of living. At 30mph that chance is reduced to 55% and, struck at 40mph there is only a 15% chance of survival. Nearly 90% of pedestrians who survive being struck by a car travelling at the urban 30mph speed limit will sustain serious injuries.

Much wider use of 20mph speed limits is needed to ensure that danger is reduced and risk more fairly distributed.

The absence of a serious casualty history does not mean a road is safe. It can mean that it is so dangerous it is avoided by unarmoured road users. Traffic speed can be used as an indicator of danger so that action is taken before casualties occur.

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