Increases in traffic speeds and intensities, associated with thedevelopment of the motorway system in the United Kingdom since the late 1950s, have accentuated the problem of vehicle-generated spray.Although some reduction in spray dispersion can be achieved by improved mudguard design, a more effective solution is to use a permeable wearing course that acts both as a sponge and as a draining layer.Pervious macadam with 20-mm aggregate was developed for roads from the 10-mm nominal size "friction course" that was developed in the 1050s to minimize aquaplaning on airfield runways. The evolution of pervious macadam has been primarily the result of a number of road trials that have led to specificaiton trials by the Department of Transport. The resulting specification for pervious macadam is included in the latest revision of British Standard 4987. The material can beexpected to have effective spray-reducing properties for 3 years for a traffic flow of 7000 commercial vehicles per day (cvd) per lane or for 6 years for 2500 cvd. To improve the long-term durability of the material and its economic viability, a road trial was started in1984 to study the performance of pervious macadams with polymer-modified binders.(A).
Samenvatting