Accidents on Rural Roads ? for Better or Worse
J Laird, ITS University of Leeds, UK; R Harris, RPS, UK
Road safety forms a major part of the benefits claimed to result from schemes to improve rural single-carriageway roads. Are existing appraisal methods well-founded ? Does improving rural roads make them safer ?
Single-carriageway A-roads in rural areas are the most dangerous routes on the highway network. Alongside journey time savings, safety improvements are one of the main benefits claimed to result from quality improvements to rural single carriageway roads.
Existing appraisal methods support the engineers? natural conviction that a better-designed road is a safer road. However, this contrasts with anecdotal evidence that as road improvements lead to increases in speeds and traffic flow, the likelihood of a fatal accident increases.
This paper examines the statistics to address the safety issue in detail - does improving these roads make them safer, or not ? Are the claimed safety benefits well-founded ?
A novel analysis is presented of accident data on the National Secondary Road network in Ireland. The Irish national secondary network consists of 2,700 km of single carriageway A-roads, complementing the national primary routes. Most of these roads are in rural areas, which face challenges of peripherality and lack of accessibility to increasingly-centralised provision of services.
For this analysis, the 34 National Secondary routes have been broken up into 850 sections, each on average around 3 to 4 km long. Each section has been allocated a road quality score based on bendiness, carriageway width and gradient. Econometric analysis of accident rates and types by road quality identifies a number of interesting characteristics.
As road quality improves, the overall accident rate falls. But the likelihood of a fatal accident increases, up to a certain threshold, before it begins to fall.
This more accurate modelling of accident rates leads to a situation where road quality improvements can result in an increase in the seriousness and the economic cost of accidents, with major implications for cost-benefit analysis of rural road improvement schemes.
The paper concludes with some thoughts on the implications of this phenomenon for transport policy.
Association for European Transport