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Road Management & Engineering Journal
Copyright © 1997 by TranSafety, Inc.
June 1, 1997
TranSafety, Inc.
(360) 683-6276
Fax: (360) 335-6402
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Systematic Process for Making Highway Improvement Decisions...
Courtesy Patrol Saves Time and Money...
Forty-Eight State Survey...
Vehicle-Arresting Net Successfully Tested...
Intersections Without Traffic Signals Symposium July 21-23, 1997



Vehicle-Arresting Net Successfully Tested in France

Thousands of trucks cross the mountains from France to Spain each day at Biarritz. Because of this heavy traffic, Roadway International chose the site as a demonstration test location for Entwistle's Dragnet vehicle-arresting system. In the September 1996 issue of World Highways/Routes du Monde, an article entitled "French Safety Net" described the test.

According to the article, the demonstration used a 44-ton (40,000 kg) truck driven at 53 miles per hour (85 km per hour). Under these test conditions, the Dragnet vehicle-arresting system (a series of safety nets) stopped the truck in less than 262 feet (80 meters). After the test, the vehicle was undamaged and the driver unharmed; the truck drove away under its own power.

Entwistle, which supplies the United States armed forces with products and technology, said it designed the safety-net system following principles used to arrest airplanes on aircraft carriers. Such vehicle safety-net systems are operational on truck ramps in Canada, Puerto Rico, Hawaii, and Illinois. The Illinois system on the Kennedy Expressway in Chicago is part of their Traffic Redirection and Access Control System for reversible lanes. Entwistle is also developing a prototype system for railroad crossings in Illinois.

At Biarritz the vehicle-arresting test system consisted of a series of nets strung across a trap formed by parallel lines of barriers. Nets stretched across the trap and attached to energy absorbers on both sides. Each energy absorber contained 197 feet (60 meters) of coiled steel tape. The vehicle striking the nets pulled the tape through a series of offset rollers, and energy was absorbed by friction and by the deformation of the steel tape. The eight staggered nets of the Biarritz system are said to be capable of safely stopping a 44-ton truck traveling 62 miles per hour (100 km/hr) on a 5 percent downgrade. To provide a safety net for cars or trucks, the design of the first net allows for arresting all vehicles from small cars to heavy trucks.

Critics of traditional truck-arresting systems say their entry angle is frequently dangerous. By contrast, crews can put the Dragnet system on the shoulder or in the median and parallel to the existing roadway--providing a safe access angle. In addition, it is claimed that the system can be installed at grade without backfill.

Roadway International felt the safety-net system was "sure to be tested" at the busy Biarritz location.

Copyright © 1997 by TranSafety, Inc.



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