Runaway truck ramp

From Wikipedia, the free encyclopedia

A runaway truck ramp on U.S. Route 60, before a left turn.

An arrester bed in Western Australia, located at the bottom of a hill before an intersection.

A runaway truck ramp or emergency escape ramp is a traffic device that enables vehicles that are having braking problems to safely stop. They are typically a long gravel filled lane adjacent to a road with a steep grade, and are designed to accommodate large trucks. The deep gravel allows the truck's momentum to be dissipated in a controlled and relatively harmless way, allowing the operator to stop it safely.

1 Design
2 Location
3 Arrester bed
4 Driver opinion
5 References
6 External links

[edit] Design

Emergency escape ramps are typically located in mountainous areas which attract high construction costs and present difficult site selection.^[1] Designs include:

Arrester bed (see below): a gravel filled ramp adjacent to the road that uses rolling resistance to stop the vehicle.
Gravity escape ramp: a long inclined path parallel to the road. A large length is required, control can be difficult for the driver, including rollback after the vehicle stops.
Sand pile escape ramp: a short length of loosely piled sand. Problems include large deceleration and the sand is affected by weather conditions (moisture and freezing).
Alternatives: such as a vehicle arresting barrier.^[2]

[edit] Location

Emergency escape ramps are usually located on steep, sustained grades, for example in mountainous areas.^[1] Long descending grades allow large 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, for example before intersections in populated areas.^[2]

[edit] Arrester bed

An arrester bed usually uses gravel/aggregate that imparts a rolling resistance on the vehicle that enters the bed.^[1] The required length of the bed depends on the speed of the vehicle, the grade of the arrester bed, and the rolling resistance provided by the gravel.^[2]

[edit] Driver opinion

A driver will generally use such a ramp only as a last resort, as doing so in the absence of a catastrophic equipment failure constitutes an admission that the driver failed to demonstrate the skill to navigate his vehicle safely down a protracted and/or steep stretch of road, which is considered a critical skill in the profession. Of course, choosing to utilize the ramp once in such a contingency situation is far more acceptable than having a major wreck.