Research Report 107 Safety benefits of median barriers on New Zealand motorways

Published: 1998

The report details the safety benefits achieved by the installation of median barriers on the New Zealand motorway system. Before & After analysis, using log-odds, regression and multiplicative models, was applied to determine the safety benefits.

Each of these models produced evidence of similar reductions in fatal accidents of around 75%, The estimated reduction in non-fatal accidents was inconclusive, with analysis showing the possibility of either a major increase or minor decrease in the number of non-fatal accidents.

Benefit/cost calculations were performed by applying both the 1986 and the 1991 methods for evaluating the benefit/cost of roading projects used in New Zealand. Median barrier installation on average had a benefit/cost ratio between 12 and 16. Because of changing accident patterns the recommendation is that, rather than developing a Median Barrier Installation Warrant based on previous experience for New Zealand motorways, each median barrier installation proposal should be judged on its own merits.