Highway route markers are the modern-day equivalent of milestones. Unlike traditional milestones, however, which (as their name suggests) were originally carved from stone and sited at one-mile intervals, modern highway route markers are made from a variety of materials and are almost invariably (except in the United States, where miles are used) spaced at intervals of a kilometre or a fraction thereof.
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Until the beginning of the twentieth century, highways were usually named rather than numbered.[1] 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.[2]
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 route identifiers often have the route identifier marked on them.
Location identification is achieved by the highway route markers having numbers on them – usually the distance from some reference point. Highway route markers invariably have a location identifier marker on them.
A highway may be divided into more than one sector, with different sector having different numbering sequences (though it is possible, as will be explained later for two sectors to share a sequence). Sector boundaries could be the boundaries of a state (as is the case of the United States Interstate highway system), or could be the middle of a large town or any one of a number of other locations.
Each numbering sequence is defined by its reference point and all the numbers within one sequence having a fixed relationship to the reference point and hence to each other (such as being at 0.1 km intervals). The reference point might be the start of the highway, it might be the start of the sector or it might be some artificial point that is located before the start of the highway. Such artificial points include the Zero Milestone in Washington, D.C. and Charing Cross in London.
In some countries such as Spain or the United States, highway Exit number are identified using location identifiers.
If a highway is rerouted, then invariably its length changes. This can be handled in one of three ways:
Until the advent of dual carriageways, it was seldom necessary to identify the actual carriageway. When this was necessary, the carriageway was often identified informally in terms of the town or city to which the carriageway is heading or by using one of the points of the compass. However, the use of highway route markers to pinpoint accidents made it necessary to identify the correct carriageway in an unambiguous manner so that the emergency services could get to the scene of the accident with minimal delay.
These route marker examples have been chosen because each has a novel feature over and above route and location identification.
Major British roads have marker posts at 100 metre intervals. These posts, which are used for administrative purposes, give the distance in kilometres from some reference point. The digits on the posts are not designed to be used by the general public. There are no fixed rules for such reference points: they may be the centre of a city, an administrative boundary or follow some other rule. Marker posts on motorways also have arrows that point to the closest emergency telephone. The markerpost in the picture is on a trunk road, not a motorway and hence has no arrow. It is however unusual in that it has the highway identifier (A38) and carriageway identifier (A) in addition to the location identification (415.0).
The advent of the mobile phone required a government rethink regarding marker posts. This has led to the erection of driver location signs in England (but at the time of writing, not in Scotland, Wales or Northern Ireland) [4] at about 500 metre (about 1/3 mile) intervals on many motorways.
Driver location signs have three pieces of information:
The location is identical to the location given on marker posts. The most commonly used carriageway identifiers are the letters “A”, “B”, “J”, “K”, “L” and “M”. [5] The letter “A” normally denotes the carriageway in the direction of increasing location numbers (usually away from London), “B” the carriageway in the direction of decreasing location numbers while “J”, “K”, “L” and “M” denote junction slip roads.
As the name suggests, the Dutch hectometre markers are spaced at 100 m intervals. In addition to having the motorway number and location on them, they also have a carriageway identifier – Li for Links (Left) and Re for Rechts (Right). The carriageways are identified as being left-hand and right-hand as viewed by somebody looking in the direction of increasing location numbers. By and large, Dutch location numbers increase as one moves away from Amsterdam, or in the case of roads that do not originate in Amsterdam, location numbers increase as one moves eastwards away from the North Sea. Carriageway identifiers “a”, “b”, “c” and “d” are used to identify slip roads on and off the motorway.
Another novel concept on Dutch hectometre markers is that speed limits are displayed on the marker boards when speed limit is not the national default of 120 km/h. This is shown on the accompanying illustration. Pictures of the normal boards can be found in main article.
California uses a postmile[6] system on all of its state highways, including U.S. Routes and Interstate Highways. The postmile markers indicate the distance a route travels through individual counties, as opposed to mile markers that indicate the distance traveled through a state.
New York reference markers are plates 252 mm by 200 mm (10 by 8 in approx) that have three rows of numbers. Since the lettering is small (60 mm, 2.4 in), they are designed for use by highway engineers rather than motorists. The first row displays the route number, the second row the NYSDOT Region, and the third row the control segment and distance from the segment start. The control segment has one digit while the distance from the start of the segment has three digits and is given in units of tenths of a mile.
To be added
The Indian route markers carry a number of different distances. The marker illustrated carries the following information:
Although the sign illustrated uses Latin script, a number of Indian location markers use the Indian national language Hindi.
This section contains examples of route markers that have fewer than three pieces of information only.