March 17, 2004
Refer to: HSA-10/B-109B
Mr. Michael J. Burkett
Burkett Moulding, Incorporated
21 Hamilton Street
Monroeville, Ohio 44847
Dear Mr. Burkett:
A recycled plastic offset block (called the P-Block) for use with strong steel post W-beam guardrail was accepted for use on National Highway System (NHS) on November 7, 2002, (Federal Highway Administration ((FHWA)) acceptance letter B-109). A similar design for use with round wood posts was accepted on August 29, 2003 (acceptance letter B-109A). Both letters were addressed to Mr. Daniel J. Mushett with Interstate Timber Products Company.
In your March 9, 2004, letter to Mr. Richard Powers of my staff, you advised him that you have purchased the rights to the P-Block from Interstate Timbers Products Company and have further modified its design. You indicated that your modified block is comprised of the same materials as the P-Block (approximately 50/50 blend of High Density Polyethylene and Low Density Polyethylene with a small amount of additives), but that the flared “wings” centered along the back edge of the block have been lengthened from their original 7 inches to 12 inches. The traffic face of the block remains approximately 4-inches wide and its effective depth remains at just under 8 inches. These details are shown on the enclosed drawing (Enclosure 1). You had this redesigned block crash tested at E-TECH Testing Services, Inc. in Rocklin, California, the results of which are contained in that agency’s March 2003 report entitled “NCHRP Report 350 Crash Test Results for the Burkett Molding P-Block Guardrail Blockout.” Enclosure 2 is the summary page from the report that shows the 2000P pickup truck was fully contained and smoothly redirected following an impact into a strong post W-beam guardrail installation in which the modified P-Block was used in lieu of standard routed timber blockouts.
I agree that the modified P-Block, as described above, is acceptable for use with strong post
W-beam guardrail installations on the NHS. Minor modifications to the dimensions of the
P-Block for use with Thrie-beam guardrail (longer block and wings) and with round wood posts (concave backside to match the posts) are also acceptable.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
(original signed by Hari Kalla)
John R. Baxter Director, Office of Safety Design
Office of Safety
Safety Home | FHWA Home | Feedback