Cross Slope
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Cross Slope
Cross slope, cross fall or camber is a geometric feature of pavement surfaces: the transverse slope with respect to the horizon. It is a very important safety factor. Cross slope is provided to provide a drainage gradient so that water will run off the surface to a drainage system such as a street gutter or ditch. Inadequate cross slope will contribute to aquaplaning. On straight sections of normal two-lane roads, the pavement cross section is usually highest in the center and drains to both sides. In horizontal curves, the cross slope is banked into superelevation to reduce steering effort and lateral force required to go around the curve. All water drains to the inside of the curve. If the cross slope magnitude oscillates within , the body and payload of high (heavy) vehicles will experience high roll and lateral vibration. Cross slope is usually expressed as a percentage: :\text = \frac \times 100\%. Cross slope is the angle around a vertical axis between: * the horizontal ...
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Drainage Gradient
Drainage gradient (DG) is a term in road design, defined as the combined slope due to road surface cross slope (CS) and longitudinal slope (hilliness). Although the term may not be used, the concept is also used in roof design and landscape architecture. If the drainage gradient is too low, rain and melt water drainage will be insufficient. This results in water pooling on the road surface, thereby increasing the risk for hydroplaning Aquaplaning or hydroplaning by the tires of a road vehicle, aircraft or other wheeled vehicle occurs when a layer of water builds between the wheels of the vehicle and the road surface, leading to a loss of traction (engineering), traction tha ... and wet-pavement vehicle crashes. Minimum drainage gradient Most road design manuals require drainage gradient to exceed 0.5%, in order to drain water and prevent excessive skid accidents. One exception to the minimum 0.5% DG limit can be found in the Norwegian road design manual, where the min ...
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Drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging (anaerobic conditions that harm root growth), but many soils need artificial drainage to improve production or to manage water supplies. History Early history The Indus Valley Civilization had sewerage and drainage systems. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered gravity sewers, which lined the major streets. 18th and 19th century The invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753. Current practices Simple infrastructure such as open drains, pipes, and berms are still common. In modern times, more complex structures involving substantial earthworks and new technologies have been common as well. Geotextiles New storm water drainag ...
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Street Gutter
A street gutter is a depression that runs parallel to a road and is designed to collect rainwater that flows along the street diverting it into a storm drain. A gutter alleviates water buildup on a street, allows pedestrians to pass without walking through puddles, and reduces the risk of hydroplaning by road vehicles. When a curbstone is present, a gutter may be formed by the convergence of the road surface and the vertical face of the sidewalk; otherwise, a dedicated gutter surface made of concrete may be present. Depending on local regulations, a gutter usually discharges, as a nonpoint pollution source in a storm drain whose final discharge falls into a detention pond (in order to remove some pollutants by sedimentation) or into a body of water. Street gutters are most often found in areas of a city which have high pedestrian traffic. In rural areas, gutters are seldom used and are frequently replaced by a borrow ditch. When urban streets do not have sanitary sewers, stree ...
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Ditch
A ditch is a small to moderate trench created to channel water. A ditch can be used for drainage, to drain water from low-lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. Ditches are commonly seen around farmland, especially in areas that have required drainage, such as The Fens in eastern England and much of the Netherlands. Roadside ditches may provide a hazard to motorists and cyclists, whose vehicles may crash into them and get damaged, flipped over, or stuck and cause major injury, especially in poor weather conditions and rural areas. Etymology In Anglo-Saxon, the word ''dïc'' already existed and was pronounced ("deek") in northern England and "deetch" in the south. The origins of the word lie in digging a trench and forming the upcast soil into a bank alongside it. This practice has meant that the name ''dïc'' was given to either the excavation or the bank, and evolved to both the words "dike"/" ...
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Aquaplaning
Aquaplaning or hydroplaning by the tires of a road vehicle, aircraft or other wheeled vehicle occurs when a layer of water builds between the wheels of the vehicle and the road surface, leading to a loss of traction that prevents the vehicle from responding to control inputs. If it occurs to all wheels simultaneously, the vehicle becomes, in effect, an uncontrolled sled. Aquaplaning is a different phenomenon from when water on the surface of the roadway merely acts as a lubricant. Traction is diminished on wet pavement even when aquaplaning is not occurring. Causes Every vehicle function that changes direction or speed relies on friction between the tires and the road surface. The grooves of a rubber tire are designed to disperse water from beneath the tire, providing high friction even in wet conditions. Aquaplaning occurs when a tire encounters more water than it can dissipate. Water pressure in front of the wheel forces a wedge of water under the leading edge of the tire, ...
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Cross Section (geometry)
In geometry and science, a cross section is the non-empty intersection (set theory), intersection of a solid body in three-dimensional space with a Plane (geometry), plane, or the analog in higher-dimensional spaces. Cutting an object into slices creates many parallel cross-sections. The boundary of a cross-section in three-dimensional space that is parallel to two of the Cartesian coordinate system, axes, that is, parallel to the plane determined by these axes, is sometimes referred to as a contour line; for example, if a plane cuts through mountains of a raised-relief map parallel to the ground, the result is a contour line in two-dimensional space showing points on the surface of the mountains of equal elevation. In technical drawing a cross-section, being a Planar projection, projection of an object onto a plane that intersects it, is a common tool used to depict the internal arrangement of a 3-dimensional object in two dimensions. It is traditionally crosshatched with th ...
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Cant (road/rail)
The cant of a Rail transport, railway track or camber angle, camber of a road (also referred to as superelevation, cross slope or cross fall) is the rate of change in elevation (height) between the two rails or edges of the road. This is normally greater where the railway or road is curved; raising the outer rail or the outer edge of the road creates a banked turn, thus allowing vehicles to travel round the curve at greater speeds than would be possible if the surface were level. Rail Superelevation in railway tracks ;Importance of superelevation In curved railway tracks, the outer rail is elevated, providing a banked turn. This allows trains to navigate curves at higher speeds and reduces the pressure of the wheel flanges against the rails, minimizing friction and wear. The difference in elevation between the outer and inner rails is referred to as cant in most countries. ;How superelevation works The main functions of cant are the following: * Improve distribution of th ...
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Foot (unit)
The foot (standard symbol: ft) is a Units of measurement, unit of length in the imperial units, British imperial and United States customary units, United States customary systems of metrology, measurement. The prime (symbol), prime symbol, , is commonly used to represent the foot. In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since international yard and pound, an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters. Historically, the "foot" was a part of many local systems of units, including the Ancient Greek units of measurement, Greek, Ancient Roman units of measurement, Roman, Chinese units of measurement, Chinese, Units of measurement in France before the French Revolution, French, and English units, English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm and 335 mm and ...
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Camber Angle
Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the creation of steering and suspension (vehicle), suspension. If the top of the wheel is further out than the bottom (that is, tilted away from the axle), it is called positive camber; if the bottom of the wheel is further out than the top, it is called negative camber. Effect on handling Camber angle alters the Automobile handling, handling qualities of some suspension designs; in particular, negative camber improves grip in corners especially with a Double wishbone suspension#Short long arms suspension, short long arms suspension. This is because it places the tire at a better angle to the road, transmitting the Centrifugal force#Examples, centrifugal forces through the vertical plane of the tire rather than through a Shear strength, shear force across i ...
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Geometric Design Of Roads
The geometric design of roads is the branch of highway engineering concerned with the positioning of the physical elements of the roadway according to standards and constraints. The basic objectives in geometric design are to optimize efficiency and safety while minimizing cost and environmental damage. Geometric design also affects an emerging fifth objective called "livability", which is defined as designing roads to foster broader community goals, including providing access to employment, schools, businesses and residences, accommodate a range of travel modes such as walking, bicycling, transit, and automobiles, and minimizing fuel use, emissions and environmental damage. Geometric roadway design can be broken into three main parts: alignment, profile, and cross-section. Combined, they provide a three-dimensional layout for a roadway. * The alignment is the route of the road, defined as a series of horizontal tangents and curves. * The profile is the vertical aspect of th ...
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