Shoulder (road)

From Free net encyclopedia

A hard shoulder or simply shoulder is a reserved area alongside the verge of a road or motorway. Generally it is kept clear of all traffic. In the event of an emergency or breakdown, a motorist can pull into the hard shoulder to get out of the flow of traffic and obtain an element of safety. A hard shoulder also allows some extra flexibility should a motorist need to take evasive action, as it is a buffer area between the main thoroughfare and the edge of the road. Emergency vehicles such as ambulances and police cars may also use the shoulder to bypass traffic congestion. These uses lead to the alternate names breakdown lane and emergency lane.

The shoulder is usually slightly narrower than a full traffic lane. In some cases, particularly on old rural roadways, shoulders do not exist or are made of gravel rather than hard asphalt or concrete. These are known as soft shoulders in comparison. Because the road surface changes at that point, they are less safe if they need to be used for emergency maneuvers, so modern practice is to build a hard shoulder whenever possible. To save money, the hard shoulder is sometimes not paved to the same thickness as the through lanes, so if vehicles were to attempt to use it as a through lane regularly, it would rapidly deteriorate. The shoulder also often collects various bits of debris that can make driving there unsafe.

Drivers will sometimes drift into the shoulder when being overtaken by passing vehicles, particularly on two-lane roads. However, it is extremely unsafe, as well as illegal, to abuse the hard shoulder by 'undertaking': passing vehicles that are nearer the centre of the road. (Some roads and expressways have a hard shoulder that is of such a narrow width that 'undertaking' is impossible.) In some jurisdictions, buses are allowed to drive on the shoulder to pass traffic jams (some observers call this a crude form of bus rapid transit). Driving in this manner requires an extremely high level of attention, however. For instance, buses are allowed to drive on the shoulder in the Minneapolis-St. Paul region of Minnesota, but in most cases, the shoulder is only one foot (30 cm) wider than the buses themselves. In Ontario, Highway 403 had its shoulders between Hurontario Street and Erin Mills Parkway widened in 2003 so they serve a dual-purpose as bus lanes and accident lanes.

On many roads, the shoulder disappears for short periods, particularly near exits and sometimes when going across bridges where the cost savings outweigh the disadvantages of not having the shoulder. However, some roads have a narrow shoulder for significant distances. This makes it difficult for large vehicles to pull into the hard shoulder altogether. The Jingjintang Expressway in northeastern China is an example. Its hard shoulder is 2.4 metres wide—not enough for some automobiles. As a result, some motorists are forced to pull out, ending up in a position that occupies half of the carriageway (rightmost lane) and half of the hard shoulder. This often results in traffic jams and sometimes worse incidents.

Image:Californiashoulderbreak.jpg In Ireland, the hard shoulder is demarcated by road markings in the form of a single dashed yellow line (solid line on motorways), possibly with the addition of yellow cat's eyes (green when a junction is upcoming and the shoulder is temporarily closing). In the USA, the right-hand shoulder is separated by a solid white line, and the left-hand shoulder (if the road is a divided highway) is separated from the main road by a solid yellow line. On freeways in foggy parts of California, there is an obvious break in the line of the shoulder before every exit; this is to help drivers find their exits in heavy fog.

Hard shoulders in the United Kingdom

Full width hard shoulders are usually provided only on motorways and are usually 3.3 metres wide, but there are exceptions. Some motorways do not have hard shoulders at all (for example the A6144(M) and the A57(M)) and there are a small number of dual carriageway A-roads which do posess hard shoulders (for example, parts of the A1, A2 and A27). Hard shoulders are always marked with a reflectorised solid white line which is 20 cm wide and is provided with a rumble strip. A line of red cat's eyes is also used, and is placed to the side of the line.

Sometimes, a hard shoulder will be coloured differently (usually red) to that of the main carriageway lanes. This is sometimes because the hard shoulder has not been resurfaced recently. The red colouring of many shoulders is because red surfacing was cheaper than black when the surface was laid. Sometimes, hard shoulders are coloured red to make it stand out from the main carriageway (for example on many of the motorways in Lancashire.)

On many modern non-motorway roads, a hard strip is provided. These are usually 1 metre wide, and are bounded by thinner solid white lines, and often without a rumble strip.de:Standstreifen fr:Bande d'arrêt d'urgence nl:Vluchtstrook sv:Vägren pl:Pas awaryjny