This report draws on literature and crash data analysis to identify and quantify geometric road design elements which contribute to casualty crash occurrence and severity on rural roads, e.g. lack of sealed shoulders, steep downhill grades combined with curves, roadsides with narrow offset to roadside hazards, and high-flow rural at-grade intersections. These findings were supported by a before and after evaluation of casualty crash reductions expected from shoulder sealing, pavement widening and road realignment. Combining this evidence and inputs by the Austroads Road Design Task Force, the report proposes a number of possible changes to Austroads road design guides aimed at reducing the casualty crash risk on rural roads. Most proposed changes involve clarification of guidance, e.g. for selection of design speed in challenging alignments, use of speed limits to control speeds, use of sealed shoulders, selection of barriers and clear zones, and greater guidance for design of low speed roundabouts. A commentary is provided discussing the usefulness of different types of evidence in revision of road engineering guidance. It is intended to make it easier for policy makers to select and commission the most appropriate inputs for consideration. (Author/publisher)
Abstract