Highway route markers

A highway location marker is the modern-day US equivalent of a milestone. Unlike traditional milestones, however, which (as their name suggests) were originally carved from stone and sited at one-mile intervals, modern highway location markers are made from a variety of materials and are almost invariably spaced at intervals of a kilometre or a fraction thereof (except in the United States, and United Kingdom where miles are still used on roadways). In other countries they may be known as driver location signs, milestones or kilometre stones.

Until the beginning of the twentieth century, highways were usually named rather than numbered. In most cases they had the name of the town or city to which they headed, for example The Old Portsmouth Road. Other ancient highway names include The Pilgrims Way, Watling Street and the Via Appia.

However, with the increase in private traffic after the First World War a simpler way of identifying roads was needed. Different countries adopted different ways of identifying roads. Under the 1966 Local Government Act Great Britain [excluding Northern Ireland] adopted a system of road numbering so that each roads had a unique number across the entire country. The relative importance of the road was identified by a “A” or a “B” prefix.

In France roads that were in the care of the national government were prefixed by “RN” (later just “N”) and had a number that was unique across all of France. Roads that were maintained by departments had a number that was prefixed by “D” and were unique within the department concerned while roads that were maintained by communes had numbers that were prefixed by a “C” were unique within a commune. The advent of motorways meant an extension to both the British and the French methods of roads identification.

Highway location markers often have the route identifier marked on them.

Location identification is achieved by the highway location markers having numbers on them – usually the distance from some reference point.

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Wikipedia