U.S. Department of Transportation Federal Highway Administration

400 Seventh St., S.W Washington, D.C. 20590

July 17

Dear Mr. Miller:

In your June 20 letter you requested formal Federal Highway Administration acceptance of the Idaho Transportation Department's 6095-mm (20-foot) long precast concrete barrier for use on the National Highway System (NHS) as a test level 3 (TL-3) barrier. To support your request, you also sent a copy of an April 2000 test report prepared by E-TECH Testing Services, Inc., in Rockland, California, entitled "NCHRP Report 350 Crash Test Results for the Idaho 6095-mm Concrete Barrier" and a videotape of the two tests that were conducted.

The barrier you tested was a standard New Jersey profile concrete barrier 8 1 O-mm (32-inches) tall and 6.095-m (20-feet) long. The base width was 610-mm (24 inches) and the top width was 150-mm (6 inches). Each segment weighed approximately 3630 kg (8000 pounds). Adjacent segments were connected using 3 1.8-mm (1.25-inch) diameter steel pins passed through four loops made from 19-mm (.75-inch) diameter steel bars. Longitudinal reinforcement consisted primarily of six no. 16 bars per segment. Two different connection designs were tested. The first consisted of galvanized 32-mm (1.25-inch) diameter by 638-mm (25-inch) long A307 hex bolts secured by 32-mm (1.25-inch) A536 heavy hex nuts. Two F844 Wide Type A washers were used, one under the bolt head and one above the nut. Enclosure 1 is a schematic drawing of this connection detail. The connection in the second test was a 32-mm (1.25-inch) diameter A36 steel pin that was 660-mm (26-inches) long. No locking nut or other pin retention device was used in this design. The steel loops were identical in both tests.

Staff members have reviewed the results of the two tests you conducted and concur with your assessment that appropriate NCHRP Report 350 evaluation criteria were met. They also agree that it is not necessary to test the 860-kg car since the barrier is identical to California's K-Rail which was successfully tested with the small car. The summary results of each test are shown in Enclosure 2. Maximum permanent deflection was 1 .O m with the bolted connection and 1.1 m with the pinned connection. The test installation was 73.2 m long and the pickup truck impacted 1.2 m from the mid-point in both tests. Impacts nearer the ends of an installation would be expected to increase the deflection distance under similar impact conditions. Based on these test results, the Idaho Concrete Barrier, with either the bolted pin connection or the drop-pin connection, may be considered acceptable for use as an NCHRP Report 350 TL-3 barrier on the NHS when such use is requested by a State transportation agency. I understand that this design remains nonproprietary and that anyone wanting to obtain detailed specifications and plan sheets for this barrier (can request them by calling you directly at (208) 334-8475.,

Sincerely yours

Frederick G. Wright, Jr.
Program Manager, Safety