Cost-effective infrastructure measures on rural roads

Monash University Accident Research Centre - Report No. 217

Authors:  J. Oxley, B. Corben, S. Koppel, B. Fildes, N. Jacques, M. Symmons, I. Johnston

Full report in .pdf format [760KB]

Abstract:

Rural road safety accounts for a considerable share of the total road safety problem, with up to two-thirds of all road fatalities occurring on rural roads. This is mainly due to higher operating speeds, hazardous roadsides and generally poorer road geometry compared to urban roads, multi-functionality and lower enforcement levels. The physical features of the road play a major role in determining mobility and crash and injury risk, and infrastructural improvements have the potential to create a safer travel environment whilst maintaining mobility. 

This report provides a review of current international literature in regard to road infrastructure and how it can be improved to reduce the frequency and severity of rural road crashes. The findings were used to compile a set of recommendations for cost-effective infrastructure measures. The following features of rural roads were shown to increase the risk of serious injury: the presence of roadside hazards such as trees and poles; intersections and their design and operational features; alignment and design speeds; and road surface conditions. 

Single-vehicle crashes are common on rural roads and mostly involve vehicles leaving the roadway and colliding with rigid objects or overturning. Measures to address single-vehicle crashes include: i) treatments to reduce speeds and speeding; ii) improved road and shoulder surfaces; iii) lane widening; iv) bridge or culvert widening; v) improved delineation of edge-lines, centre-lines and lane-lines; vi) geometric improvements to curves; vii) roadside barriers; and, viii) clearing of roadside hazards (including establishment of 'clear-zones'). 

Multi-vehicle collisions are also an important source of road trauma in rural areas and include collisions at intersections, head-on impacts and rear-end collisions. Measures to address multi-vehicle crashes include: i) treatments to reduce speeds and speeding; ii) geometric improvements to intersections including conversion to roundabouts, grade-separation, improved channelisation, sight distance, and medians; iii) geometric improvements to road lengths including use of crashworthy barrier systems or medians and delineation; iv) conversion of undivided roads to divided roads; v) geometric improvements to curves; and, vi) improved road and shoulder surfaces. 

Fundamental changes to the inherent safety of the rural road system are essential. A system-wide and comprehensive application to key crash problems in rural areas appears to offer the most effective and cost-effective solutions. The most strategically important measures to reduce crash and injury risk are: i) introduction of grade-separated intersections; ii) construction of roundabouts; iii) installation of crashworthy barrier systems; and, iv) introduction of speed reduction measures.

Sponsoring organisation: Swedish National Road Administration (SNRA)