Southwest Research Institute® (SwRI®) News

Self-restoring Traffic Barrier

San Antonio, TX -- Sept. 24, 1981 -- A versatile new highway guardrail of unusual design is capable of handling impacts of vehicles ranging from 2,100-lb. mini cars to 40,000-lb. intercity buses, and of doing it in a way that minimizes demands on limited highway system maintenance funds.

This Self-Restoring Traffic Barrier has been chosen as a winner in the 1981 I-R 100 Awards competition conducted by Industrial Research & Development, officials of the publication announced Thursday in Chicago. These awards are presented for developments honored as the 100 most significant technological advances of the year.

The innovative barrier design was developed by Southwest Research Institute® (SwRI®), a not-for-profit applied research and engineering organization based in San Antonio, in a program conducted for the Federal Highway Administration (FHWA).

Maurice E. Bronstad, highway research manager in the SwRI Department of Structural Engineering, is principal developer. Charles F. McDevitt, FHWA contract manager, also contributed to the design effort.

The barrier is called "self-restoring" because its design permits it, in most cases, to absorb the impact of a vehicle leaving the road, and to return to its original position after safely redirecting the vehicle within the roadway.

The horizontal beam of this barrier is suspended from pivot bars that lean outward from a row of upright posts. These pivot bars are hinged at top and bottom, at attachments to the post and the top of the beam. At the top of each bar, the beam is supported by a flexible cable that permits the railing to move freely to the rear.

When hit by a vehicle, only this first stage is needed, and the beam returns to its original position by action of gravity.

For heavier vehicles, the beam continues to pivot upward until it reaches the erect posts, which provide a very strong second stage barrier.

In full-scale crash tests using remotely controlled vehicles driven into this barrier at 60 miles per hour and an angle of 15 degrees, Institute engineers reported successful containment and redirection of vehicles including a 2,100-lb. mini car, a 20,000-lb. school bus, and a 40,000-lb. intercity bus. All were driveable after leaving the barrier.

Need for development of a new barrier was based on recognition of a move by many agencies across the country toward replacement of flexible metal barriers with rigid concrete structures, because of serious problems of costs involved in frequent repair of impact damage to metal railings. When a car strikes a rigid concrete barrier, however, the only mechanisms of protective energy dissipation available are crushing of vehicular structure, and ride-up along the barrier's side, which can lead to rollover.

The new design provides more "forgiving" protection for motorists while not requiring significant maintenance, says Bronstad, who likes to refer to the self-restoring barrier by an acronym, SERB. Costs are competitive, he adds, recommending use of SERB wherever heavy vehicle containment is a serious consideration.

For more information about the Self-Restoring Traffic Barrier, contact Joe Fohn, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas, 78228-0510, Phone (210) 522-4630, Fax (210) 522-3547.

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