Citation

Elvik R. Accid. Anal. Prev. 2008; 40(3): 1200-1210.

Affiliation

Institute of Transport Economics, Gaustadalleen 21, NO-0349 Oslo, Norway.

Copyright

(Copyright © 2008, Elsevier Publishing)

DOI

10.1016/j.aap.2008.01.004

PMID

18460389

Abstract

This paper identifies nine characteristics of road safety problems that are all in principle amenable to numerical measurement. The nine characteristics identified are:



1. Magnitude -- The size of the contribution a problem makes to the total number of accidents or killed or injured road users Population attributable risk represented by a problem;

2. Severity -- The gradient of the attributable risk associated with a problem with respect to levels of injury severity Comparison of the attributable risk associated with a problem across levels of injury severity; comparing shares of injuries by levels of severity

3. Externality -- The fact that travel performed by one group of road users imposes an additional risk on other groups of road users The net contribution to the overall risk of a road user group attributable to risks imposed by other groups

4. Inequity -- The size of the contribution to risk made by a lack of proportionality between the benefits of transport and the risk run Difference in number of injuries between: (a) current distribution of risk and (b) a distribution of risk in proportion to shares of exposure

5. Complexity -- The extent to which the specific contributions of individual risk factors to the overall risk represented by a problem can be identified Complexity is indicated by: (a) many factors each making a small contribution to overall risk; (b) correlations among factors preventing their unique contributions from being identified; (c) interactions among risk factors with respect to their effect on accident rate (d) “over-determination”, i.e. the sum of known factors more than explain overall risk

6. Spatial dispersion -- The degree to which an accident problem is concentrated geographically Distance between accident concentrations that have been identified statistically

7. Temporal stability -- Changes over time with respect to the magnitude of a road safety problem A time-series of the population attributable risk represented by a problem

8. Perceived urgency -- The strength of the support in the population for stronger action or regulations designed to solve a problem Results of opinion polls regarding the support for stronger action to solve specific road safety problems

9. Amenability to treatment -- The prospect of implementing effective safety treatments, i.e. treatments that will reduce a problem (in particular its magnitude)

The purpose of identifying these dimensions and of trying to measure them is to provide a basis for selecting problems for treatment by means of safety programmes. Selecting problems for treatment usually cannot be done on the basis of a single dimension, as it is the mix of characteristics that determine the prospects for successfully treating a problem. It is proposed that amenability to treatment is a function of complexity, perceived urgency and the availability of cost-effective treatments. Speed and speeding is used as an example of a road safety problem to illustrate how the various dimensions can be measured.

Language: en