`Sustainable Safety' and the categorisation of the Dutch road network.

In the Netherlands, a major national road traffic safety programme under the title `Sustainable Safety' was initiated by the Dutch government in 1997. An underlying and fundamental principle of Sustainable Safety is a reclassified road network comprising essentially only two urban and three rural road categories or classes. As part of the programme there is an ongoing research project aimed at defining road and other design elements that visually distinguish the different road classes, making them recognisable to the road user and thereby provoking the correct road user behaviour. The objective of the project is to investigate how the road layout can be best designed to ensure that the intended official classification corresponds to the perception of road users (in particular, car drivers). In an experiment four road layout alternatives were investigated by means of a sorting task in which subjects had to sort photographs of road scenes on the basis of expected road user behaviour on the road (i.e. roads where similar behaviour was expected should be sorted into one category). No restrictions were made and subjects could sort the material into any number of road classes they deemed fit. Road layout elements were varied among the different road categories to investigate which one would lead to a classification similar to the official classification. One of the alternatives was a baseline design layout already widely adhered to in the Netherlands, incorporating certain preliminary guidelines. In the other three layouts a number of relevant visual elements were added or altered. A cluster analysis was performed on the data. The results showed that the categorisation of one specific design layout - not the baseline variant - was almost in complete agreement with the official classification. In this layout edge markings as well as so-called `counter stream markings' had been added so as to increase the differences between the different road categories. For the covering abstract see ITRD E113725 (C 22328 CD-ROM).