The purpose of this paper is to draw together research and developments in the use of wide single 2+1 (WS2+1) carriageways in the UK over the last 12 years. Following research by the Scottish Office between 1993 and 1995, the Highways Agency carried out research between 1995 and 1997 to explore the potential for increased use of single carriageway roads on the trunk road network in England. It reviewed previous studies on the operation and safety of single carriageways, and investigated European experience of roads marked as WS2+1. The study concluded that WS2+1 layouts have the potential to provide benefits in safety and operational terms, but as there was no experience of their use in the UK, it recommended that evaluation schemes should be implemented to monitor their performance prior to inclusion as a standard layout in the Design Manual for Roads and Bridges (DMRB). As a result, two WS2+1 schemes were implemented and their performances monitored. The schemes are the A68 Soutra Hill in Scotland opened in February 2002 and the A303 Ilminister Bypass in England opened in June 2003. Early monitoring results indicate that both schemes are meeting their objectives. This has given the UK Overseeing Organizations the confidence to start work on a new national standard for WS2+1 roads.
Samenvatting