The report reviews the major changes that have occurred in the surface course materials used in the United Kingdom during the 1990s. Until the mid-1990s, most asphalt surfacing was carried out at nominal thicknesses of 40 mm or greater in hot rolled asphalt or dense bitumen macadam. Prior to that, there had been surfacings that could be laid at lesser thicknesses but none were widely used. In 1991, trials of French thin surfacings were started whilst SMA trials started from 1994. From these trials and later ones, thin surfacing systems were accepted as a surfacing that now provides the majority of material used in the UK. Initially, the proprietary products were approved by the Highways Agency but this is being superseded by BBA-HAPAS certification. The products may develop further into generic materials with the expected introduction of CEN standards for thin asphalt concrete and Stone Mastic Asphalt. The paper was first published by the Institution of Asphalt Technology in `The Asphalt Yearbook 2001', when it was awarded the annual Argent Award for the best paper. The paper has subsequently been updated. (Author/publisher)
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