Since 1982 a research program observing the long-term behavior of porous asphalts under normal traffic conditions has been carried out at the institute for transportation, traffic, highway and railwayengineering ivt of the swiss federal institute of technology in zurich. In a first phase, an observation program measured skid resistance, permeability, rolling tire noise, and deformation once or twice a year on a selection of porous asphalt pavements already in service. The general appearance and behavior under winter conditions were also recorded. In a second phase, the research was extended to include the study of material properties such as aging of the binder, performance of the mix, and so forth. The emphasis in this paper is given to results from the first phase of the research program. Particular attention is devoted to the problems of skid resistance, permeability, noise reduction, and behavior under winter road conditions of porous asphalt pavements. For these parameters, the methods of measurement, results, and general conclusions are presented. Conclusions are provided separately for two potential areas of application of porous asphalt: motorways and other roads with fast traffic, and urban roads with slower traffic. Taking into account the different advantages and disadvantages of porous asphalt, experiences obtained so farare generally very positive about the application of porous asphaltto roads with high-speed traffic. When applied in urban areas, different problems appear and initial advantages may be lost within a short time. Also applications in an urban environment cannot take fulladvantage of the noise-reducing potential when traffic travels at lower speeds. Results from this research project also indicate that anumber of conventional surface layers can have favorable acoustic properties; in this field there is potential for further development.Under winter road conditions, porous asphalt surfaces can present the same range of variation of skidding properties as conventional surface layers. However, at a particular moment, there is a differencein the behavior of the two pavement types along the road at the site where the type of surface changes. This paper appears in transportation research record no. 1265, Porous asphalt pavements: an international perspective 1990.
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