Prioritising harm elimination: the effect of benefit-cost metrics and planning timeframes on perceived benefits

Benefit-cost analysis is extensively used to justify and prioritise road infrastructure investment but its reliance, when applied to road safety initiatives, can be counter-productive. Due to their substantial costs, primary Safe System-aligned treatments that virtually eliminate harm often come with low benefit-cost ratios (BCRs) and it can take many decades for their benefits to mature. The aim of this study is to compare the benefits of high-BCR supporting treatments and low-BCR primary treatments over both short- and long-term planning timeframes. The results show that primary treatments provide greater long-term benefits but require adequate investment for these benefits to be realised.