Hard shoulder

A hard shoulder or simply shoulder is a reserved area alongside the verge of a road or motorway. Generally the hard shoulder 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, 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 smaller than the width of 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 near 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.

On many roads, the shoulder disappears for short periods, particularly near exits and sometimes when going across bridges. 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 in width—not wide 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.

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. In the UK there is a solid white line, and on a motorway this will be reinforced by cat's eyes and a rumble strip. 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 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.nl:Vluchtstrook sv:Vägren