POROUS ASPHALT WEARING COURSES IN THE NETHERLANDS: STATE OF THE ART REVIEW

Since 1972, research has been carried out in the Netherlands to assess the advantages of porous asphalt wearing courses in relation to conventional pavement structures. Efforts have also been made to quantify the extra costs incurred by road managing authorities when using such materials. The chief advantages of porous asphalt wearing courses to road users are expected to be improved road safety and reduced congestion. Furthermore, the noise nuisance on such roads is greatly diminished. On the other hand, additional costs are involved because of the shorter service life and more expensive maintenance required for porous asphalt, as well as the fact that thicker asphalt constructions are needed to provide the necessary bearing capacity. Based on a cost-benefit analysis, it has been shown that the extra expenditure associated with porous asphalt can be justified by the potential benefits. The Dutch Department of Public Works (Rijkswaterstaat) has therefore decided to install such wearing courses where possible on the national road network, particularly on motorways. The characteristic properties of porous asphalt and the related financial implications are discussed in this paper. Moreover, an outline is given of how the new policy of the Department of Public Works, which will take some 10 years to implement, has been developed.