This research, which was carried out in New Zealand in 2013, used computer simulation modelling to identify whether it is better to rectify or replace existing roadside crash barriers that are of substandard height or are corroded, or to install new roadside crash barriers at locations with significant hazards where there are currently no barriers. This information would assist road controlling authorities in establishing spending options and priorities.
The computer simulation modelling quantified the effects of barrier height on crash severity for a selected range of barrier types (W-beam/wooden post and wire rope), vehicles (models, speeds and paths) and physical contexts. Crash severity costs were also derived for a limited selection of rectified and reinstalled barriers, new barriers in the same locations; and new barriers at untreated locations that have significant hazards.
The key finding was that for both barrier types there was an effect on increasing crash severity with barrier heights that were lower than specifications. However, this was not generally found to be severe, even for height differences thought to exceed those expected to occur on the New Zealand state highway network. The research results suggested that in many cases (especially for wire-rope barriers) it would be much more cost effective to install new barriers at previously untreated locations than to raise existing barriers to the correct heights.