High Quality Content by WIKIPEDIA articles! A road number is often assigned to a stretch of public roadway. The number chosen is often dependent on the type of road, with numbers differentiating between interstates, motorways, arterial thoroughfares, two-lane roads, and so forth. In some countries, such as the United Kingdom, the road number has a letter followed by a number of up to 4 digits. For example, the main road from London to Edinburgh is called the A1, the "A" in Britain indicating a first class route; this is classified as being more important than "B" roads. The A2, A3, A4, A5, A6 also radiate out from London to points around the coast.