between regional towns and cities. In Great Britain, the A1, A2, A3, A4, A5 and A6 radiate out from London, or nearby, (in clockwise order) to points around the coast. Some A-roads, or sections of A-roads, are dual carriageway, without being full motorways; some sections upgraded to motorway standards are designated in the form A1(M). B roads are minor roads; they may connect small towns and villages, or offer an alternate route to major roads. Classified unnumbered roads, unofficially called C roads, are smaller roads typically connecting unclassified roads with A and B roads. Unclassified roads are roads intended for local traffic; 60% of UK roads are unclassified, and the 200,000 miles of B, unnumbered, and unclassified roads constitute 87% of total road length in the UK. All classified roads in England and Wales starting in the zone between the A1 and the A2 begin with the figure 1 (e.g. A137, B1412), etc. Scotland is similarly divided into zones by the A7, A8 and A9 which radiate out from Edinburgh. Zones are not used in Northern Ireland. Motorways Motorways are classified as "special roads", and are numbered in a similar, but not identical, manner. Motorways are either M-class or upgraded A-road, A(M) class. M-class motorways are labelled in the form Mx, as a higher grade of motorway, and A(M) roads are labelled in the form Ax(M), where x is the designation of the road, dependent on the zone. For example, the M25 is the London Orbital Motorway, and the A1(M) is the upgraded A1 dual carriageway. A similar clock-face zonal system is used in many other European countries (for example, Spain and Belgium). United States In the United States, numbered highways belong to one of three or more systems of numbered routes, depending on the state. There are two national-level route numbering systems, the older United States Numbered Highway System laid out in 1920s, and the newer Interstate Highway System started in the 1950s. Additionally, every state in the U.S. maintains its own set of numbered state highways. Some states have other systems as well, either a system of numbered county highways or secondary state highways. A few cities also have numbered city highways; for example, the city of Charlotte, North Carolina, maintains Charlotte Route 4. The U.S. Highway System, indicated by a white shield with black numbers, is based on a numbering grid, with odd routes running generally north–south