August 24, 2004

Refer to: HSA-10/B-128

Mr. Byron Berger
Acting Chief
Roadside Safety Technology Branch
Materials Engineering and Testing Services
5900 Folsom Boulevard
Sacramento, California 95819-4612

Dear Mr. Berger:

In Mr. Sudhakar Vatti's July 12 letter, he requested formal acceptance by the Federal Highway Administration of a see-through, combination steel post and beam bridge rail called the California ST-20S. This design, shown in Enclosure 1, was based on a previously accepted Wyoming DOT design for a test level 4 (TL-4) bridge rail and a modified version of your crash-tested ST-20 design. In your test, there was some hood snagging observed with the pickup truck, so you increased the rail face to post face distance in the ST-20S to reduce the likelihood of this occurrence. The final ST-20S design consists of four horizontal box-beam rail elements, the top and bottom ones being TS 203 x 76 x 7.9 structural tubes, and the middle two being TS 203 x 102 x 7.9 tubes. The summary results of the test you ran are shown in Enclosure 2.

Since your design uses thicker steel plate posts, has a greater rail offset then the Wyoming TL-4 rail, and has a lesser opening between the lower rail elements, you did not believe it necessary to conduct the small car test. Similarly, because the ST-20S is 1185-mm high (excluding the additional 187-mm tall top bicycle rail) versus the 830-mm high Wyoming design, you did not conduct the single-unit truck test. I concur that both of these tests can be waived based on the performance of the Wyoming design and on the differences between the two designs.

Therefore, the ST-20S design may be considered an NCHRP Report 350 bridge rail at TL-4 and used on the National Highway System when selected by the appropriate transportation authority. I assume that anyone needing detailed drawings and material specifications can obtain this information directly from your office.

Sincerely yours,

(Original Signed By R. Powers)
for:
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety

2 Enclosures