RUNAWAY TRUCK RAMP

A 'runaway truck ramp', 'runaway truck 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, gravel-filled lane adjacent to a road with a steep grade, and is 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.

Contents

Design

Location

Arrester bed

Driver opinion

References

External links

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 upwardly-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 being affected by weather conditions (moisture and freezing).

★ 'Alternatives': such as a vehicle arresting barrier.^[2]

Location

Emergency escape ramps are usually located on steep, sustained grades, for example in mountainous areas. 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, for example before intersections in populated areas.

Arrester bed

An arrester bed usually uses gravel/aggregate that imparts a rolling resistance on the vehicle that enters the bed. 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.

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.

References

1. Full-Scale Arrester Bed Testing Leads to More Cost-Effective Design, DOT Arizona, , , TR News, 1993
2. Design Manual - Auxiliary Lanes, , , , Washington State Department of Transportation, May 2006,

External links

★ Design considerations

★ Truck escape ramps from www.usroads.com

★ European road design (search for "arrester bed")