Report numberRA-MOW-2009-006
TitleA computational model to assess the impact of policy measures on traffic safety in Flanders: Theoretical concepts and application
AuthorsBetty Nambuusi
Elke Hermans
Tom Brijs
Published byPolicy Research Centre for Mobility and Public Works, track Traffic Safety 2007-2011
Number of pages40
Document languageEnglish
Partner(s)Universiteit Hasselt
Work packageOther: Policy organisation ans monitoring

The aim of this report is to describe the development of a computational model to assess the effect of policy measures on safety at the regional level and compare their costs and benefits in order to select measures with the most beneficial cost-benefit ratios. The main stages of the model include the reference situation, the baseline prognosis, the measure prognosis, the savings and the cost-benefit analysis. The reference situation describes the current traffic performance and safety situation. The baseline prognosis takes the future change in traffic performance and autonomous risk into account. The measure prognosis relates to the situation after applying measures. The number of savings is the difference between the baseline and the measure prognosis. The cost-benefit analysis is used to determine whether the benefits of a measure outweigh its costs. This analysis helps to compare measures with a different life span and to make a choice between possible combinations of measure sets.


The model incorporates several road and intersection categories in the region yet the illustration in this report relates to only one road category (being highways). The model focuses on developments in the future, thereby quantifying the effect of measures applied either at a regional or a locational level. Regional measures are assumed to have an impact on road safety in the entire region while locational measures have an impact on road safety at the location they are applied. During the development of the model, several sets of measures were tested. Besides, a number of important developments on which the user of the model has no influence such as the change in traffic performance and in autonomous risk are taken into account. The autonomous risk change captures the collective learning process caused by the growing knowledge of the road safety problem, the constant improvement of the safety performance of the road transport system, better equipped motor vehicles and roads, the improvement of road safety education and, increasing legislation and enforcement. Future changes in traffic performance are represented by growth scenarios. Here, two growth scenarios (GS1 and GS2) are studied for the period 2005-2030. Also, a case study is carried out for a period of four years (2003–2006) on highways in Flanders to illustrate the methodology. The safety situation in terms of the number of saved casualties during the four years is assessed taking into account general developments i.e growth in traffic performance and autonomous risk. The cost-benefit analysis is only discussed in theory but not illustrated in this report since the aim of the first analysis concerns assessing the effectiveness of measures in terms of the number of saved casualties.


The developed model allows the user to get insight into the impact of different regional and locational measures applied at certain moments in time. This report describes the methodology of the computational model and some first illustrative results. In the future, the model will be improved to account for dependency among measures. Also, a sensitivity analysis will be carried and the most unsafe areas in the region will be displayed by linking it to a geographical information system.

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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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