August 29, 2003

HSA-10/B-109A

Mr. Daniel J. Mushett
Interstate Timber Products Co.
111 Garnet Lane
Oak Ridge, Tennessee 37830

Dear Mr. Mushett:

Your recycled plastic offset block (P-Block) for use with strong steel post w-beam guardrail was accepted for use on the National Highway System (NHS) on November 7, 2002, (Federal Highway Administration (FHWA)) acceptance letter B109).

In your July 11, 2003, letter to Mr. Richard Powers of my staff you requested acceptance of a similar offset block for use with round wood posts, an alternative strong post w-beam guardrail system used by some State Departments of Transportation. You indicated that the modified block (PC-Block) is comprised of the same materials as the P-Block (50/48 blend of High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) with 2 per cent blowing agent), but has modified dimensions to fit the round wood post. Specifically, the traffic face remains 4-inches wide and its effective depth has been retained at 7.65 inches, but the field side of the block has an approximate 3.5-inch radius to fit against the standard 7-inch diameter round wood posts. These details are shown on the enclosed drawing.

I agree that this block is acceptable for use with strong, round post w-beam guardrail installations on the NHS. Please note the following standard provisions that apply to FHWA letters of acceptance:

• This acceptance is limited to the crashworthiness characteristics of the offset block and does not cover its long-term durability.
• Any changes that may adversely influence the crashworthiness of the device will require a new acceptance letter.
• Should the FHWA discover that in-service performance reveals unacceptable safety problems, or that the device being marketed is significantly different from the version that was accepted, it reserves the right to modify or revoke its acceptance.
• You will be expected to certify to potential users that the blocks furnished have essentially the same chemical composition and geometry as that submitted for acceptance.
• To prevent misunderstanding by others, this letter of acceptance, designated as number B-109A shall not be reproduced except in full. This letter, and the documentation upon which this letter is based, is public information. All such letters and documentation may be reviewed at our office upon request.
• If your product is patented, it cannot be specified for use on Federal-aid projects, except exempt, non-NHS projects. Our regulations concerning proprietary products are contained in Title 23, Code of Federal Regulations, Section 635.411, a copy of which is enclosed.

Sincerely yours,

(original signed by John R. Baxter)

John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety

2 Enclosures