A runaway truck ramp is a traffic device that enables vehicles which are having braking problems to safely stop.It is typically a long, sand- or gravel-filled lane connected to a steep downhill grade section of a main road, and is designed to accommodate large trucks or buses.
source/image(PrtSc): Engineering and architecture
The ramp allows a moving vehicle’s kinetic energy to be dissipated gradually in a controlled and relatively harmless way, helping the operator to stop it safely without a violent crash.
Emergency escape ramps are usually located in mountainous areas which cause high construction costs and present difficult site selection.A ramp may cost US$1 million.Designs include:Arrester bed,Gravity escape ramp,Sand pile escape ramp,Mechanical-arrestor escape ramp.
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Long descending grades can 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 radius of curvature of the road, or before a place that may require the vehicle to stop, such as before an intersection in a populated area.The placement criteria can vary from one region/country to another.
