- 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
- Emergency vehicles such as ambulances and police cars may also use the shoulder to bypass traffic congestion
- Active traffic management, used on busy multi-lane roads, may allow 'hard shoulder running' by general traffic at reduced speeds during periods of high traffic volumes.
- In some places a 'Bus bypass shoulder' may be provided which allows bus services to pass stationary traffic
- Shoulders, especially paved or hard shoulders provide additional space should a motorist need to take evasive action or need to recover control of their vehicle before a run-off-road collision occurs.
- In some urban areas, shoulders are used as travel lanes during peak commuting hours.* Shoulders may provide space for bicyclists to ride out of vehicle traffic
- In areas without sidewalks, pedestrians may walk on shoulders
- On curbed roadways, shoulders move the gutter away from the travel lanes which reduces the risk of hydroplaning, and reduces splash and spray of stormwater onto pedestrians using an adjacent sidewalk.
- Shoulders move water away from the roadway before it can infiltrate into the road's subbase, increasing the life expectancy of the road surface.
- Shoulders provide structural support of the roadway
General characteristics 
The shoulder is usually slightly narrower than a full traffic lane.
In some cases, particularly on older rural roadways, shoulders that do exist 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. Notable the section of Ontario Highway 401 between Windsor and London had soft shoulders with a sharp slope which was blamed for facilitating vehicle rollovers, if drivers accidentally drifted off of the paved section of the road and then overreacted upon hitting the gravel. Modern practice is to build a hard shoulder whenever possible. The U.S. Federal Highway Administration encourages the placement of a Safety Edge — a 30° compacted taper on the end of the pavement dropoff — to ensure that any vehicle running off the edge of the roadway is better able to maintain control while trying to steer back onto the pavement.
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 road 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 often 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.)
On many roads, the shoulder disappears for short periods, particularly near exits and sometimes when going across or under bridges or tunnels 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 of this phenomenon. Its hard shoulder is 2.4 metres wide, which is not wide enough for some automobiles. As a result, some motorists are unable to fully exit the mainline when they need to pull over, so they end up in a position that is halfway in the rightmost lane and halfway in the hard shoulder. The result is often a traffic jam and occasionally a collision.
Bus bypass shoulder 
In some jurisdictions in the United States and Canada, buses are allowed to drive on the shoulder to pass traffic jams, which is called a bus-only shoulder or bus-bypass shoulder (BBS); the term "bus-only shoulder lane" is incorrect from a technical and legal standpoint.
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. In the Minneapolis-St. Paul region of Minnesota, over 270 miles of shoulder have been designated for use by buses. The Route 9 BBS in Central New Jersey runs along two stretches of shoulders are dedicated for exclusive bus use during peak hours. The bus lanes, which run for approximately 3-mile (4.83 km) are the first component of a planned 20-mile (32.19 km) BBS corridor.
Peak period use by all traffic 
On specially signed sections of highway in the Boston Metro Area, cars are allowed to use the shoulder as they would a normal lane during morning and evening rush hours. The same scheme is employed elsewhere, such as on Interstate 66 in Virginia between the Capital Beltway and US-50.
In the UK, usage of the hard shoulder is known as hard shoulder running. A pilot project on an 11-mile stretch of the M42 motorway, near Birmingham began in September 2006. Special signage, new laybys and a variable speed limit have been put in place to improve safety. This has proved very successful, with journey times decreasing by 26% northbound and 9% southbound. Drivers can also better predict their journey times as the variability decreased by 27%. The average accident rate dropped from 5.2 to 1.5 per month. It has also proved popular with motorists, 60% of whom want to see it expanded to other English motorways. The system has been expanded to the M6, with plans to implement it to parts of M1, M25, M60 and M62 by 2015.
Increased cyclist safety 
Direct rear impacts with cyclists are a more prominent collision type in arterial/rural road type situations. When they occur in such circumstances they are also associated with significantly increased risk of fatality. Data collated by the OECD indicates that rural locations account for 35% or more of cycling fatalities in Denmark, Finland, France, Great Britain, Japan, the Netherlands, and Spain.
The use of appropriately designed segregated space on arterial or interurban routes appears to be associated with reductions in overall risk. In Ireland, the provision of hard shoulders on interurban routes in the 1970s reportedly resulted in a 50% decrease in accidents. It is reported that the Danes have also found that separate cycle tracks lead to a reduction in rural collisions.
Characteristics in various countries 
Republic of Ireland 
Full-width hard shoulders are provided on most new, upgraded (from the 1980s onwards), and major national roads in the Republic of Ireland, especially on wide two-lane and dual-carriageway roads (the shoulders on most 2+1 roads are narrow however). They are defined within the official document the Rules of the Road as a part of the road that should normally only be used by cyclists and pedestrians. Their provision of on interurban routes in the 1970s reportedly resulted in a 50% decrease in accidents involving pedal cyclists.
The hard shoulder is usually demarcated by road markings in the form of a single dashed yellow line with the addition of yellow cat's eyes. On motorways, and at critical points on other routes (e.g. between junctions or sliproads, or beneath overpasses) a solid yellow line is used, denoting additional restrictions on usage of the hard shoulder. At junctions and sliproads, the yellow line peels away into the turn, with a dashed white line (with green cats' eyes) denoting a lane division following the main route (i.e. in most cases the road remains the same width, and a turn lane takes the place of the hard shoulder).
In the 2000s, Bus Éireann coaches were allowed to use the hard shoulders on national roads into Dublin. However, dedicated bus lanes are now present on sections of some routes, such as the N7 Naas Road, and such use of actual hard shoulder is not universal.
United States 
The right-hand shoulder is separated by a solid white line, and the left-hand shoulder (if the road is one-way, such as part of a divided highway) is separated from the leftmost through lane by a solid yellow line. On many roads the lines are supplemented by reflective raised pavement markers placed every few feet in order to provide additional visual and tactile feedback to drivers crossing the lines.
Normally one is not allowed to drive on the shoulder but in the case of traffic block, use of the shoulder is allowed for the purpose of reaching an exit if the exit is within 200 feet.
On freeways in foggy areas 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 (especially dangerous tule fog).
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 A57(M)) and there are a small number of dual carriageway A-roads which do possess 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 cats' 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.
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.
The shoulder located on the side of Italy's highway is normally used as emergency lane in case of breakdown or is used by emergency vehicles in case of queues. According to the regulation in force it is mandatory wear a high visibility jacket when dismounting from the vehicle stopped on emergency lane.
Normally one is not allowed to drive on the shoulder but in case of traffic block, use of the shoulder is allowed to reach an exit if the exit is within 500 metres.
In a similar manner to Italy and the United States, as described above, the shoulders located on the side of Australia's highways are normally used as an emergency lane in the case of a breakdown or by emergency vehicles in the case of road congestion. However, no mandatory regulations exist to wear a high visibility jacket when dismounting from the vehicle stopped in an emergency lane.
A recent study conducted by the National Coroners Information System (NCIS) in Australia  has revealed twenty-nine (29) closed case fatalities (and at least a dozen case fatalities still under coronial investigation) that had been reported to Australian coroners where a person was "struck in an emergency lane after their vehicle had stopped" between July 2000 and November 2010.
See also 
- Federal Highway Administration. "Safety Edge Introduction - Every Day Counts". Retrieved 2013-01-22.
- "A shoulder to drive on". Traffic Technology Today. Retrieved 2013-04-01.
- Bus-Only Shoulders (Minnesota Department of Transportation)
- Bus-Only Shoulders in Minneapolis-St. Paul
- "NJDOT to open Route 9 Bus shoulder lanes in Old Bridge" (Press release). New Jersey Department of Transportation. November 29, 2006. Retrieved 2012-03-03.
- Synthesis 64: Bus shoulder lanes, Transportation Research Board of the National Academies, 2007
- Baldwin, Zoe (July 10, 2009). "New Jersey gradually clearing away obstacles to bus rapid transit". Mobilizing the Region. Tri-State Transportation Campaign. Retrieved 2014-04-04.
- Extra lane' plan to be extended BBC News
- Hard shoulders opens on busy M6 by Birmingham BBC News
- HIGHWAYS AGENCY News Release issued by COI News Distribution Service on 21 March 2011
- Figure IV.7 Pedestrian and cyclist accidents by road type. RS7:Safety of Vulnerable Road Users, Organisation for Economic Co-operation and Development, August 1998
- The bicycle, a study of efficiency usage and safety., D.F. Moore, An Foras Forbatha, Dublin 1975
- Collection of Cycle Concepts, Danish Roads Directorate, Copenhagen, 2000
- "Art 162 Codice della Strada". Archived from the original on 2008-06-06. Retrieved 2007-06-12.
- National Coroners Information System, NCIS
- Deaths in Emergency Lanes - National Coroners Information System (NCIS) Fact-Sheet, January 2011