Northern Ireland's oldest dual carriageway is the Sydenham Bypass which was begun in 1938 and finally opened in 1959. Since large scale motorway building ceased in the mid 1970s, many new dual carriageways have been built. For the purposes of this web site, a dual carriageway is defined as a road where traffic travelling in opposite directions is separated by some form of barrier. Some small sections of dual carriageway are omitted in order to make the site manageable.