November 7, 2002

HSA10/B109

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

Dear Mr. Mushett:

In your September 6 letter to Mr. Richard Powers of my staff you requested acceptance of a recycled plastic offset block for use with strong post, metal beam guardrail on the National Highway System (NHS).You stated that your block is comprised of a 50/48 blend of High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) with 2 per cent blowing agent.Subsequent to discussions with Mr. Powers, you modified the shape of your block and sent him a revised drawing on October 22.This final design is shown in the Enclosure to this letter.

Based on staff recommendations and your product's similarity to several previously accepted designs, I agree that your block may be considered equivalent to a routed timber offset block and may be used with strong post w-beam guardrail installations on the NHS.As with all recycled material offset blocks, this acceptance is based on the anticipated crash performance of the w-beam barrier when your block is used and is not intended to address its durability.It is also based on the assumption that all production blocks will be of the same materials and dimensions as noted herein.

Sincerely yours,

(original signed by Harry W. Taylor)

for:

Carol H. Jacoby, P.E.
Director, Office of Safety Design

Enclosure