Casualties and collisions are associated with a whole range of different social and economic costs. Traditionally, the cost of the provision or repairs needed in the immediate aftermath of a collision were the only type of costs to be quantified. At the national level, there is now specific guidance and supporting methodologies for both quantifying and calculating the cost of different injury severities and collision scenarios. Such support allows for an estimation of the social costs associated with the burden of road traffic injuries (RTIs) to society. Estimations of different casualty and collisions costs allow authorities and road safety stakeholders to better evaluate the effectiveness of interventions in the pursuit of the Safe System and contribute to the evidence base. Estimations for the cost of specific casualty types (slight, serious and fatal) and collisions are provided by the Department for Transport (DfT) on an annual basis, alongside methodology updates.
An established method to evaluate the cost effectiveness of an intervention is cost-benefit analysis (CBA). CBA as a method of evaluation aims to directly compare the costs and benefits of different options measured in monetary units, with options being considered cost effective if the net benefits gained are greater than the net cost incurred. The results from the cost-benefit analyses are usually quantified by benefit-cost ratios (BCRs) The benefit-cost ratio of an intervention is an indicator of cost effectiveness – the ratio of the total present value of benefits to the total present value of costs, considered over the timespan of the analysis. A BCR greater that 1 indicates that the benefits outweigh the cost and that it is worth considering for investment purposes. This type of analysis makes it easier for decision makers to assess competing alternatives and make informed investment choices. First-year rate of return (FYRR) is often used to compare investment options and interventions. This refers to the benefits minus the operating costs in the first year of operation of an intervention, discounted to year zero, divided by the present value of investment costs. FYRR can indicate whether an intervention’s optimal implementation time is in the past or future, and hence whether deferral is warranted.
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