Parking lot
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Parking lot is the American English term that refers to a cleared area that is more or less level and is intended for parking vehicles. Usually, the term refers to a dedicated area that has been provided with a durable or semi-durable surface. In British English and other Commonwealth Englishes, parking lots are known as car parks which is usually applied to a surface car park, as opposed to a multi-storey car park.
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General information
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The usual parking lot in the United States is paved with asphalt. Some are paved with concrete. Many are gravel lots. A few of the newer lots are surface with permeable paving materials.
Parking lots have their own special type of engineering. While parking lots have traditionally been an overlooked element of development projects by governmental oversight, the recent trend has been to provide regulations for the configuration and spacing of parking lots, their landscaping, and drainage and pollution abatement issues.
Environmental considerations
Runoff handling
Parking lots have certain characteristics that set them apart from roadways in terms of their engineering and operating requirements. The first is that they often cover large contiguous areas with impermeable paving surface. This means that virtually all of the rain (minus evaporation) that falls becomes runoff. The parking lot must be built to effectively channel and collect that runoff. Traditionally, the runoff has been shunted directly into storm sewers, streams, or even sanitary sewers. However, most larger municipalities now require retention basins to catch runoff to reduce the stress on sewer systems or streamways.
Water pollution
Parking lots also tend to be subject to contamination with concentrated spots of pollutants such as motor oil. While motor vehicles on roadways may drip oil, they do so over a large area. Oil drips on parking lots are concentrated enough that they can have a deleterious effect on the water quality of the runoff. Other pollutants, even brake-lining dust, rust particles, and other particulate materials that settle on the parking lot surface, can be a similar problem. Therefore, an important second function of the retention basin for parking lots is to act as a temporary storage impoundment to allow particulate materials to settle out and to slow or even prevent the release of other pollutants into waterways.
In some places, the water is not channeled into retention basins, but into dry wells.
Alternative paving
An alternative solution today is to use permeable paving surfaces, such as brick, stone, special paving blocks, or tire-tread woven mats. The intent of these is to allow precipitation falling on the surface to soak into the ground through the spaces inherent in the parking lot surface. The ground then may become contaminated in the surface of the parking lot, but this tends to stay in a small area of ground, which effectively filters water before it seeps away.
Parking lot landscaping
Many areas today also require minimum landscaping in parking lots. This usually principally means the planting of trees to provide shade. Customers have long preferred shaded parking spaces in the summer, but parking lot providers have long been antagonistic to planting trees because of the extra cost of cleaning the parking lot.
However, parking lots represent significant heat islands and, indeed, heat sinks in urban areas. The heat from paved areas in urban zones has been shown to even have the power to change the weather locally. By providing trees or other means of shading parking lots, the heat and glare resulting from them can be significantly reduced.
Parking standards
Many municipalities also have established minimum spacing standards for parking lots, the standards depending on whether the parking is parallel, pull-in, or diagonal, and depending on what types of vehicles are allowed to park in the lot or a particular section of it. Codes also usually specify that a given parking lot must have a certain minimum number of spaces, depending on the floor area in a store, or how many bedrooms in an apartment complex.