Report numberRA-MOW-2011-014
TitleSelecting road safety indicators for Flanders by using the road safety target hierarchy
AuthorsBrenda Wilmots
Elke Hermans
Tom Brijs
Hans Tormans
Published byPolicy Research Centre for Mobility and Public Works, track Traffic Safety 2007-2011
Number of pages98
Document languageDutch
Partner(s)Universiteit Hasselt
Work packageOther: Risk assessment

Road safety is an important topic to study, given the human suffering and costs that road crashes cause. Nowadays, the road safety status of a country or region is usually described by registered crash data. Moreover, quantitative targets are set with regard to these data. Although crash and casualty data are relevant, in this report we wish to obtain a broader view on the road safety problem. This, by taking into account various related and underlying aspects that influence the road safety level in a country or region. Improvements in these aspects help reduce the number of road safety crashes and casualties. In this report we use quantitative and qualitative measures (so called ‘road safety indicators’) to capture these different aspects. We select road safety indicators starting from the theoretical framework of the target hierarchy for road safety (e.g. Morsink et al., 2005).


The road safety target hierarchy consists of different levels (from top to bottom): social costs, road safety output (final outcomes), road safety performance (intermediate outcomes or SPI’s), road safety measures and programmes (policy output) and structure and culture (policy input). Relations between the levels of the hierarchy are assumed, where underlying indicators influence indicators at the level(s) above. We use this framework in this report, because it gives insight in the processes that lead to crashes and casualties and social costs. By consulting international and national literature, more insight in this framework is gained and the framework is further explored for Flanders. The final goal of this report is to create an indicator set that captures the different layers of the road safety hierarchy, that can then be used to monitor progress. To achieve this goal road safety indicators are listed on the different levels of the hierarchy for Flanders. Next, the indicator candidates are evaluated based on eight criteria (understandable, measurable, available data, etc.). Based on the data related criteria (available, reliable, comparable/coherent), a distinction between best available indicators and best needed indicators for Flanders is made. Contrary to the best available indicators, no data, no reliable data or no comparable data are (publicly) available for the ideal indicators. The focus of the evaluation of indicators lies on the following levels of the road safety target hierarchy: final outcomes, intermediate outcomes and policy output.


The final best available indicator sets includes 1 indicator related to the social costs of road unsafety, 2 road safety output indicators, 11 safety performance indicators (SPI’s), 46 indicators for policy measures and programmes and 11 possible policy input indicators. The finale ideal indicator set contains 2 indicators related to the social costs of road unsafety, 1 road safety output indicators, 15 SPI’s, 47 indicators for policy measures and programmes and 11 possible policy input indicators. The social costs express the consequences of road unsafety in terms of monetary values. The road safety output indicators, are indicators with regard to crashes and casualties that are disaggregated by severity, age, vehicle type, etc. and expressed with respect to an exposure measure. The SPI’s were selected by starting from the seven risk domains defined in the European SafetyNet project, namely: alcohol & drugs, speed, protective systems, daytime running lights, vehicle, road infrastructure and trauma management. For each risk domain, at least one best available and one ideal indicator is selected. For the formulation and evaluation of policy output indicators we started from the measures identified in the Flemish road safety plan. For the bottom level, indicators with regard to values and norms, functional (political) structure and physical structure are listed. At this layer of the target hierarchy no separate evaluation takes place, only possible indicators for which Flemish data are available, are listed. They are not real road safety indicators, yet underlying indicators with a specific influence on road safety.


For each layer a data overview is given for the ‘best available indicators’. Different sources (like FOD Economie, MORA, etc.) are consulted to collect these data. 


The presented indicator sets in this report give insight in the complex phenomenon of road safety in Flanders and its different aspects. In the future, further data collection is possible by contacting different administrations. Because data availability is a problem (especially for certain layers), it is also important to study the possibility to collect indicator data for the ‘ideal indicators’ in the future. That way, the presented indicator sets can be updated. Furthermore, the presented indicators can be used to monitor the evolution in road safety and its subaspects.

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The Policy Research Centre for Traffic Safety carries out policy relevant scientific research under the authority of the Flemish Government. The Centre is the result of a

cooperation between Hasselt University, KU Leuven and VITO, the Flemish Institute for Technological Research.


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