How to trade safety against cost, time and other impacts of road safety measures.

Public policy, including road safety policy, involves balancing competing values against each other. Several techniques of policy analysis, most prominently cost-benefit analysis, have been developed to help policy makers prioritize between different values. Valuation studies have not produced credible monetary values of life and limb. Cost-benefit analysis therefore cannot tell when the "right" balance has been struck between road safety and other objectives of transport policy. All formal tools of policy analysis are likely to reflect analyst values to a major extent, not the values of policy makers only. It is argued that policy choices and tradeoffs can be informed simply by providing factual information about impacts and not attempting to impose any value judgements. A widely applicable metric is to state impacts as changes in human longevity and health state.