Relationships between road safety, safety measures and external factors

A scan of the literature in view of model development and topics for further research


Churchill, T.; Norden, Y. van




The purpose of this literature scan is to examine where literature on the effect of external factors and road safety measures on road safety exists and where it is lacking. This scan will help us to decide which factors to include in a comprehensive road safety model as SWOV is working on, and at the same time identifies promising future research topics. The report is divided into two main road safety topics; firstly, the external influences which are not directly related to road safety management but do affect road safety and, secondly, road safety measures which aim to improve road safety. External influences that affect road safety have been reviewed by SWOV in six exploration studies; the factors that have been identified by SWOV as relating to road safety are: - Social and cultural factors - Spatial planning and policy - Public health - Economy - Mobility - Technology and environmental protection - Other factors As a response to the generated road safety situation the mitigating impact of measures to improve road safety are also of interest in order to model road safety, for both descriptive and predictive purposes. For this reason the influence of individual road safety measures also needs to be identified to improve estimates of road safety. The SWOV book The summit conquered (De top bedwongen in Dutch; SWOV, 2007) incorporated a selection of the most commonly studied three external influences: demographics, mobility, and modal split, which are the point of departure for the SWOV model of road safety, and goes on to list and describe the various road safety measures that have been applied in the Netherlands during the period 1950 to 2005. Road safety measures can be grouped into broad categories as follows: - Infrastructural measures o Physical measures o Road rules - Vehicle safety o Primary safety o Secondary safety - Enforcement, promotion, and education SWOV wants to understand certain developments in how society could influence or even had influenced road safety, and also how the actions taken to improve road safety affect the resulting safety situation. Understanding of all of these relations is required to understand developments in road safety in the past and to obtain better predictions for future developments of road safety. The purpose of this study is two fold. Firstly, the summary of known causal relationships between external influences and road safety measures, respectively, and road safety outcomes in terms of casualties or collisions is presented. These relations can be used for the development of a road safety model. Secondly, knowledge gaps will be identified as well as future research possibilities. As research results fill knowledge gaps the road safety model can be improved with additional relations to safety outcomes, casualties or crashes. The literature scan is presented largely in tabular format for easy reference by topic, and separated by external influences or road safety measures to compliment the structure of the external influence exploration studies and The summit conquered. To summarize the findings a table of available literature as well as knowledge gaps is provided. The report concludes with a short discussion. This report is intended as a “quick” scan of the literature to guide initial efforts in model development and future research rather than a totally comprehensive literature review. Literature reviews in conjunction with future work are recommended to provide a more thorough and up to date view of the literature, and a specific focus on the details required for the selected model of road safety. In addition to being a scan of the literature this report may be useful as a framework for recording which developments have been included in the model, to which degree, and what remains to be done. Although the information contained in this report will be important in the determination of the areas in which to focus research, the framework for a transparent research selection tool remains an important next step.

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