September 5, 2003 

Refer to: HSA-10/B-107 

Mr. Robert D. Slagter

President

ANRO Timber Products, Incorporated

7887 Ashwood Drive, SE 

Ada, Michigan 49301 

Dear Mr. Slagter: 

In your May 23 letter to Mr. Richard Powers of my staff, you requested the Federal Highway 

Administration’s (FHWA) acceptance of a recycled plastic block, called the Anro block, for use 

with strong steel-post w-beam guardrail on the National Highway System (NHS). Subsequently, 

you had the Anro block tested at the Midwest Roadside Safety Facility and sent us a copy of that 

agency’s report, “Performance Analysis of the Anro Timber Products Recycled Plastic Spacer 

Block”, dated August 25, 2003. Based on comparison bogey vehicle tests of a standard wood 

block and the Anro block, both mounted on W150 x 13.5 steel posts, the report concluded that 

there was no substantial difference in performance between the two offset blocks. 

The Anro block is an injection-molded product composed of approximately 60 per cent recycled 

polyethylene (PE), 40 per cent polypropylene (PP), and a maximum of 2 per cent blowing agent. 

 Each block is nominally 100-mm (4-inches) wide for 162 mm (6.38 inches), and then flares out 

to a post-side width of 150 mm (6 inches) over the last 41 mm (1.62 inches). A 108-mm x 

10-mm (4.25-inch x 0.38-inch) routing on the backside fits over the steel post flange. The bolt 

hole dimensions are 0.875-inches in diameter at the rail side, tapering uniformly to a 0.742-inch 

diameter at the post side. These and other dimensions are shown on the enclosure. 

After reviewing the test results, I consider the Anro block acceptable for use with strong post 

w-beam barrier on the NHS when it conforms to the dimensions, and is composed of the same 

materials, as noted above and as shown in the enclosure. Please note that the following 

provisions apply to this acceptance: 

• Any material or dimensional changes that may adversely influence the crashworthiness of 

the device will require a new acceptance letter. 

• This acceptance is based solely on the expected impact performance of the Anro block 

and is not intended to address the long-term performance or durability of the product. 

Furthermore, it shall not be construed as authorization or consent by the FHWA to use, 

manufacture, or sell any device that may be patented by others. The FHWA is neither 

prepared nor required to become involved in issues concerning patent law. Patent issues, 

if any, are to be resolved by the parties involved. 

• Should the FHWA discover that in-service performance reveals unacceptable safety 
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problems, or that the device being marketed is significantly different from the version 

described herein, it reserves the right to modify or revoke its acceptance. 

• You will be expected to certify to potential users that the blocks you supply have 

essentially the same chemistry, mechanical properties, and geometry as noted above. 

• To prevent misunderstanding by others, this letter of acceptance, designated as number 

B-107 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. 

• The Anro block may include patented components and, if so, is considered proprietary. 

When proprietary devices are specified by a highway agency for use on Federal-aid 

projects, except exempt, non-NHS projects, they: (a) must be supplied through 

competitive bidding with equally suitable unpatented items; (b) the highway agency must 

certify that they are essential for synchronization with existing highway facilities or that 

no equally suitable alternative exists or; (c) they must be used for research or for a 

distinctive type of construction on relatively short sections of road for experimental 

purposes. 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