Road safety on rural roads
af Søren Underlien Jensen
This handbook introduces useful tools and methods for calculating the expected number of accidents and injuries when planning or redesigning existing roads and junctions in rural areas. The handbook is aimed at professionals working with road safety in road administrations and consultancy.
The handbook is based on the report Uheldsmodeller, sikkerhedsfaktorer og værktøjer for landevejsnettet , which describes road safety on rural roads and develops accident prediction models and accident modification factors that show how road safety is affected by changes of road design and traffic management.
Below is a brief introduction of the handbook contents.
To estimate accidents and injuries on a specific road network, the network must be divided into junctions and links. Definitions of junctions and links in rural areas can be found in chapter 2.
The number of accidents and injuries at junctions and on links can be estimated by the use of accident prediction models. An accident prediction model is a mathematical expression, used to describe how the number of accidents and injuries depends on different variables e.g. traffic volume. Chapter 3 describes Accident Prediction Models (APMs) for signalised junctions, roundabouts, priority junctions and links in rural areas.
When estimating accidents and injuries for links and junctions where the design differs from the designs described in Chapter 3, accident modification factors (AMFs) are used. AMFs describe how design, geometry and traffic management changes safety. The use of AMFs is described in Chapter 4.
Chapter 5 describes how APMs can be used to predict the road safety impact when redesigning existing junctions and links as well as in the planning of new roads or junctions. The chapter includes two examples of how to use the APMs and AMFs.
Two calculations tools which make it easy to estimate the number of accidents and injuries at junctions and on links have been developed. Chapter 6 includes a brief manual to the calculation tools. The calculations tools can be downloaded free of charge from the website of the Danish Road Directorate or Trafitec.