curbstone

　 　

WordNet

1. a paving stone forming part of a curb (同)kerbstone

PrepTutorEJDIC

1. (歩道の)縁石(《英》kerbstone)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/06/30 16:29:38」(JST)

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For other uses, see Curb (disambiguation) and Kerb (disambiguation).

Curb, gutter, and storm drain

A curb (North American English), or kerb (British English), is the edge where a raised sidewalk (pavement in British English) or road median/central reservation meets a street or other roadway.

History

East India House, Leadenhall Street, London, 1766. The sidewalk was separated from the main street by six bollards in front of the building. By the late 18th century, this method had largely been supplanted by the use of curbs.

Although curbs have been used throughout modern history, their widespread construction and use only began in the 18th century, as a part of the various movements towards city beautification that were attempted in the period.

A series of Paving Acts in the 18th century, especially the 1766 Paving and Lighting Act, authorized the City of London Corporation to create footways along the streets of London, pave them with Purbeck stone (the thoroughfare in the middle was generally cobblestone) and raise them above street level with curbs forming the separation. Previously, small wooden bollards had been put up to demarcate the area of the street reserved for pedestrian use. The Corporation was also made responsible for the regular upkeep of the roads, including their cleaning and repair, for which they charged a tax from 1766.

With the introduction of macadam roads in the early 19th-century, curbs became ubiquitous in the streets of London.

Function

Curbs may fulfill any or several of a number of functions. They separate the road from the roadside, and discourage drivers from parking or driving on sidewalks and lawns. They also provide structural support to the pavement edge. Curbs can be used to channel runoff water from rain or melted snow and ice into storm drains. There is also an aesthetic aspect, in that curbs look formal and "finished".

Since curbs add to the cost of a road, they are generally limited to urban and suburban areas, and are rarely found in rural areas except where certain drainage conditions (such as mountains or culverts) make them necessary. Curbs are not universally used, however, even in urban settings (see living street).

Safety

Metal forms before the concrete is poured and finished by hand

Old sidewalk with granite curb in Kutná Hora

Hand forming at catch basins

In low-speed environments, curbs are effective at channeling motor vehicle traffic. On higher speed roads, curbs should not be used because they can destabilize vehicles that strike them. A high-speed vehicle that hits a curb may actually turn towards the sidewalk, rather than be directed away from it. A vehicle that strikes a curb can be tripped into a rollover crash or vaulted into the air. The vehicle could be vaulted over a traffic barrier into the object the barrier is intended to shield. This is a reason why they are rarely used on rural or high speed roads. Where curb is used with a traffic barrier, the barrier should either be close to or well behind the curb, to reduce the chances of a vehicle going over the barrier.

Depending on the area and the distance between the travel lane and the edge of pavement, an edge line can be used to indicate the outside (shoulder) edge of the road. Retroreflective road marking material can also be applied to the curb itself to make it more conspicuous.

Types of curb

There are a number of types of curb, categorized by shape, material, height, and whether the curb is combined with a gutter. Most curb is constructed separately from the pavement, and the gutter is formed at the joint between the roadway and the curb. Combined curb and gutter (also called "curb and channel") has a concrete curb and gutter cast together in one piece. "Integral curb" is curbing constructed integrally as a part of a concrete pavement.

Shape

Curbs often have a vertical or nearly-vertical face, also called "barrier", "non-mountable", or "insurmountable curb". Vertical-faced curb is used to discourage motor vehicle drivers from leaving the roadway. The square (90°-edge) or close-to-square type is still almost always used in towns and cities, as it is a straight step down and thus less likely to be tripped-over by pedestrians. By contrast, a slope-faced curb allows motor vehicles to cross it at low speed. Slope-faced curb is most often used on major suburban thoroughfares.

At crosswalks and other pedestrian crossings, narrow dropped curb cuts are used to allow small wheeled vehicles such as wheelchairs, children's tricycles, prams, and strollers to cross. This makes it easier to traverse for some pedestrians, and especially for those in wheelchairs. Wider curb cuts are also used to allow motor vehicles to cross sidewalks at low speed, typically for driveways.

In Great Britain, "high containment kerbs" are used at locations with pedestrians, fuel station pumps, and other areas that need greater protection from vehicle traffic. These are 14 inches (36 cm) high - much higher than standard curb, with a sloped lower portion and a concave face. These are also known as "Trief" curbs.

Rounded curbs are most often used at driveways, and continuously along suburban residential streets where there are many driveways and the sidewalk has a grassy setback from the street. This type of curbing starts out nearly flat like the road, curves up in a concave manner to a gentle slope, then curves back in a convex manner to nearly flat again, making it much easier to drive over, and is also known as a "mountable curb" in some localities.

Material

Curbs are constructed of many materials, including asphalt, stone or masonry blocks, but most often are made of Portland cement concrete. The type of material may depend on the type of paving material used for the road and the desired function or need. For example, a Portland concrete curb used with an asphalt concrete road surface provides a highly visible barrier at the edge of the road surface. Other types of curb material include stone slabs, cobblestone, and manufactured pavers.

Concrete curb may be constructed by setting forms by hand, filling them, letting them set up, and then removing the forms. When large quantities of curb are to be constructed, it is often more efficient to use a slip form casting machine. Curbs can also be precast at a central location and trucked to the construction site.

Asphalt curb is usually made with a paving machine. It can be cheaper if it is formed at the same time that a road is paved, but is less durable than concrete curb.

Stone curb, often made from granite, is durable and resistant to de-icing salt. It is also chosen for aesthetic reasons. In areas where granite is available, it may be cheaper than concrete curb. One disadvantage of granite curb is that it can cut a tire sidewall if it is rough-faced.

Belgian block curbs are made by placing blocks over a concrete slip. Then, more concrete is wedged in between the blocks to hold them together. These blocks can be vertical, or angled in order to create a mountable curb.

Height

This machine slip casts a concrete curb with integral gutter

When designing a curbed roadway, engineers specify the "reveal" or "lip". The reveal is the height of the section that is visible (revealed) above the pavement surface. Typical reveals are in the 4 to 8 inches (100 to 200 mm) range. Curbs at handicapped curb cuts (or "kerb ramps", for example in Australia) should have no reveal, although Americans with Disabilities Act guidelines permit up to 0.25 inches (6.4 mm) of vertical reveal.

Most curb extends down into the ground below the pavement surface, to improve their stability over time. The total height, including the buried portion, is often 16 inches (410 mm).

Integral gutter

Curbs with integral gutters are used where better hydraulic flow performance is needed. However, this places a longitudinal joint (parallel to the direction of travel) near where bicyclists often ride. If the main roadway and gutter settle differently over time, the vertical edge that develops at the joint can cause a hazard for bicyclists.

Auto racing curbs

Curbs at the Suzuka International Racing Course

In auto racing, curbs are flat curbstones lining the corners or chicanes of racing tracks. They are often painted red and white, and are intended to prevent unauthorized short-cuts and keep the racers safely on the track. Although they are not considered part of the racing track, drivers sometimes "ride the curbs" in order to maintain momentum and gain a time advantage in cornering.

See also

• Curb extension
• Curb feeler
• Kassel kerb
• Road surface

References

English Journal

• Curbstone consultations.

• Berlin L.SourceNorthShore University HealthSystem, Skokie Hospital, IL, USA. lberlin@live.com
• AJR. American journal of roentgenology.AJR Am J Roentgenol.2011 Jul;197(1):W191.
• PMID 21700985

• Curbstone consultations.

• Berlin L.SourceDepartment of Radiology, Rush North Shore Medical Center, 9600 Gross Point Rd., Skokie, IL 60076, USA.
• AJR. American journal of roentgenology.AJR Am J Roentgenol.2002 Jun;178(6):1353-9.
• PMID 12034596

Japanese Journal

• 御影石を模擬したコンクリート二次製品の異常膨張現象

• コンクリート工学 = Concrete journal 43(12), 32-38, 2005-12-01
• NAID 10016514842

• 日比谷公園開園時における二・三の施設の石材加工・利用技術(平成17年度日本造園学会全国大会研究発表論文集(23))

• ランドスケープ研究 : 日本造園学会誌 : journal of the Japanese Institute of Landscape Architecture 68(5), 483-488, 2005-03-31
• NAID 110006655423

• 御影石を模擬したコンクリート二次製品の異常膨張現象

• コンクリート工学 43(12), 32-38, 2005
• NAID 130004399451

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