Runaway truck ramp
A runaway truck ramp, runaway truck lane, escape lane, emergency escape ramp or truck arrester bed is a traffic device that enables vehicles that are having braking problems to safely stop. It is typically a long, sand or gravel-filled lane adjacent to a road with a steep down-hill grade, and is designed to accommodate large trucks. The deep filling allows the truck's momentum to be dissipated in a controlled and relatively harmless way, allowing the operator to stop it safely.
Design
Emergency escape ramps are typically located in mountainous areas which cause high construction costs and present difficult site selection.[1] Designs include:
- Arrester bed: a gravel-filled ramp adjacent to the road that uses rolling resistance to stop the vehicle.[1] The required length of the bed depends on the mass and speed of the vehicle, the grade of the arrester bed, and the rolling resistance provided by the gravel.[2]
- Gravity escape ramp: a long upwardly-inclined path parallel to the road. A large length is required. Control can be difficult for the driver: problems include rollback after the vehicle stops.
- Sand pile escape ramp: a short length of loosely piled sand. Problems include large deceleration; sand being affected by weather conditions (moisture and freezing); and vehicles vaulting and/or overturning after contacting the sand pile.
- Mechanical-arrestor escape ramp: a proprietary system of stainless-steel nets transversely spanning a paved ramp that engage and retard a runaway vehicle. Ramps of this type are typically shorter than gravity ramps and can have a downhill grade. One such ramp at Avon, Connecticut in the United States has an electrically-heated pavement surface to prevent snow and ice accumulation.[3][4]
- Alternatives: such as a vehicle arresting barrier.[2]
Location
Emergency escape ramps are usually located on steep, sustained grades, as in mountainous areas.[1] Long descending grades allow high vehicle speeds to be reached, and truck brakes can overheat and fail through extensive use. The ramps are often built before a critical change in the curvature of the road, or before a place that may require the vehicle to stop, such as before an intersection in a populated area.[2] These can vary from one region/country to another however.
Gallery
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Runaway truck ramp east of Asheville, NC IMG 5217.JPG
Runaway ramp on Interstate 40 east of Asheville, North Carolina
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An arrester bed on Great Eastern Highway in Western Australia, located at the bottom of a hill before an intersection
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Escape Ramp In China Expwy G4511-cropped.jpg
An emergency escape ramp on the G4511 in China
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TER US 44 Westbound Avon, CT, USA.png
Mechanical-arrestor truck escape ramp (with heated pavement) on U.S. 44 westbound in Avon, Connecticut
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20141118 Misiryeong Penetrating Road (Emergency Escape Ramp)2.jpg
An Emergency Escape Ramp on Misiryeong Penetrating Road in Gangwon Province, Korea
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Emergency Escape Ramp on Misiryeong Penetrating Road.jpg
An Emergency Escape Ramp (Runaway Truck Ramp) on Misiryeong (미시령) Penetrating Road near Sokcho, Korea
See also
References
External links
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Wikimedia Commons has media related to Runaway truck ramps. |
