Abstract The “Unit Superstructure” is a new method of constructing the superstructure in traffic areas. The construction consists of a pervious surface, open aggregate and a geotextile in which rain and surface water are distributed by means of infiltration to the underlying soil. Two test areas have been constructed in Lund and tests of the Unit Superstructure have been carried out for one year. The first preliminary results from the study are presented in this paper. The investigation shows that the pervious surface is most sensitive to clogging during the period when buildings are still under construction in the area. Lorries, trucks and building machines spread soil particles and dirt on the asphalt surface. This gradually reduced the infiltration capacity. A 470 m 2 parking lot constructed with the Unit Superstructure method was exposed to heavy traffic of building machines during a period of 12 months. Subsequently, the surface was dug up in order to estimate the pollution level. Samples were taken at different levels and analyzed with respect to different constituents. Surface protection during the construction period or some kind of cleaning of the surface afterwards is a necessity. Infiltration tests from one of the oldest Unit Superstructures in Sweden are also presented in the paper.