Safety requirements for the cross sectional profile of distributor roads with an 80 km/h speed limit : recommendations for the update of the Handbook Road Design.

Single carriageway distributor roads with an 80 km/h speed limit (80km/h roads) are among the least safe roads in the Netherlands. A combination of factors are responsible, among which the road design and the spatial integration. Road design guidelines are intended to provide a specific or minimum level of road safety. However, presently these guidelines are insufficiently supported by empirical knowledge about the relation between the characteristics of road design and road safety. In addition, design guidelines are not always applied in practice. This lack of knowledge stands in the way of an accurate estimate of the road safety effects of such deviations from the guidelines. Hence, there is a definite need into the relation between the road design and road safety. Together with road authorities and knowledge partners SWOV investigated the relation between the road safety and the design characteristics of the 80km/h roads (the vertical cross section consisting of elements like carriageways, lanes, narrow shoulders, direction separators, obstacle-free zones, et cetera). This was done with the purpose of creating a scientific basis describing the relation between road design and road safety, more in particular for the ‘composition’ of the cross sectional profile by the different elements. The study was made possible by contributions from the Fund Collective Knowledge (FCO) and the Ministry of Infrastructure and the Environment. The study was divided into three sub studies: 1. a study into the actual design and implementation of cross sectional profiles in the Netherlands; 2. an (inter)national literature study into the relation between design characteristics and road safety; 3. a practical study consisting of a behavioural study and a mathematical modelling study. The latter investigated whether a Crash Prediction Model (CPM) can be developed to quantitatively describe the relation between design characteristics and crashes. This report may be accessed by Internet users at: http://www.swov.nl/rapport/D-2013-02.pdf