Development of risk models for the road assessment programme

During 2001, TRL developed a process of risk rate mapping for the European Road Assessment Programme (EuroRAP) to enable the risk of fatal and serious injury accidents occurring on different parts of the British primary road network to be compared. As a second stage of risk comparison, a risk rating system was developed which ranked road sections according to their road design features. This process initially focussed heavily on the injury protection qualities of the road design, and was described as the “Road Protection Score”.

In 2006, under the International Road Assessment Programme, the concept of an Road Protection Score rating process was further developed to enable it to be applied in low- to middle-income countries with the objective of developing cost-effective programmes of road safety countermeasures for those countries. The risk model development for these programmes was led by TRL under contract to EuroRAP and International Road Assessment Programme, and with substantial input from the EuroRAP and International Road Assessment Programme members and partners, particularly the then Swedish National Road Administration for the EuroRAP RPS process, and the Australian Road Research Board and Midwest Research Institute, Kansas, for the International Road Assessment Programme model.

This report describes the ideas behind the development of both risk models from the viewpoint of the TRL researcher leading the development process. It discusses the evidence on which the risk models were based and the comparison of their outputs with observed accident data, and suggests how these outputs should be used.