U.S. Department 

Of Transportation 

Federal Highway 

Administration

400 Seventh St., S.W. 

Washington, D.C. 20590 

October 25, 1993 

Refer to: HNG-14/SS-39 

Mr. John Owensby 

President 

Recycled Plastic Products, Inc. 

412A E. Williams Street 

P.O. Box 1603 

Apex, North Carolina 27502 

Dear Mr. Owensby: 

Thank you for your recent letter to Mr. Thomas O. Willett requesting the Federal 

Highway Administration’s (FHWA) acceptance of your company’s plastic sign post. 

Your letter was accompanied by a report dated September 1993, and a video on the crash 

testing that was conducted to assess the breakaway performance of the sign post. The 

static testing, pendulum tests, and full-scale crash tests conforming to the guidelines 

contained in the National Cooperative Highway Research Program (NCHRP) Report 350, 

“Recommended Procedures for the Safely Evaluation of Highway Features,” were 

performed by the Texas Transportation Institute. 

The acceptance requirements for breakaway supports are found in the 1985 AASHTO 

“Standard Specifications for Structural Supports for Highway Signs, Luminaires and 

Traffic Signals.” These specifications have been adopted, with minor modifications by 

the FHWA. 

The posts used in the tests were manufactured of recycled plastic and measured 89 mm x 

89 mm x 3.66 m long (3.5 inches x 3.5 inches x 12 feet). Note that spliced posts were 

used in the crash testing but are not acceptable for use in the field. A 0.6-m x 0.9-m (2-

feet x 3-feet) sign was mounted at a height of 2.1 m (7 feet) to the bottom of the sign. 

The post was embedded 0.6 m into “standard” soil and the top of the sign and post was at 

3.0 m (10 feet). 

The crash test conditions and results are summarized below: 

Test Number 0491F-1 0491F-2 

Soil Type Standard Standard 

Impact Speed, km/hr (mph) 35 (21.8) 101.4 (63.0)
Velocity Change, m/s (fps) 0.625 (2.05) 1.19 (3.96) 

Occupant Impact, m/s (fps) None N/a 

Stub Height, mm (in) None * None * 

*Post broke below ground line. 

The results of these tests meet the change-in-velocity and stub-height requirements 

adopted by the FHWA. Therefore, your company’s plastic signposts are acceptable for 

use in projects on the National Highway System (NHS), within the range of conditions 

tested, if proposed by a State. No more than one post may be used within a 2.1-m span, 

and use is limited to installations in soils, which approximate the “standard” soil in which 

they were tested. 

Because of the current technology limitations in manufacturing these posts, the 3.66-m 

long posts were fabricated from a 2.44-m length spliced to a 1.22-m length. The long end 

was the one embedded in the soil. This splice, which had a strength estimated to be no 

greater than 1/9th the strength of the solid post, was not structurally adequate to prevent 

the post from coming apart during the tests. In the high-speed tests, the middle portion of 

the fractured post penetrated the windshield. The NCHRP Report 350 states: 

“...detached elements, fragments, or other debris from the test article should not 

penetrate or show potential for penetrating the occupant compartment...” 

From our experience with wood posts we conclude that had there not been a weak splice 

in the tested post, the windshield would not have been penetrated. It is our understanding 

that you will overcome the length limitations on your product and will only market fulllength posts. Our acceptance of your breakaway post is based on this understanding. We 

emphasize that our acceptance of your company’s post in only for full-length posts with 

no splices, with a maximum of one post in a 2.1-m (7 foot) path. 

Our acceptance is also limited to the breakaway characteristics of the plastic posts and 

does not cover the structural features. Presumably, you will supply potential users with 

sufficient information on structural design and installation requirements to ensure proper 

performance. We anticipate that the States will require certification from Recycled 

Plastic Products, Inc., that the posts furnished have essentially the same composition, 

mechanical properties, and geometry (except for the splice) as those used in the tests, and 

that they will meet the FHWA change in velocity requirements. 

We understand that your company has exclusive marketing rights to these recycled 

plastic posts. Therefore, we consider them to be proprietary products. In order for 

proprietary products to be used in Federal-aid projects on the NHS 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 alternate 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, 

 Lawrence A. Staron, Chief 

 Federal-Aid and Design Division 

Enclosure 

 

Federal Highway Administration 

HNG-14:Nartimovich:gm:6-22-93:61331 

Copies to: 

HPD-1 HNG-1 HNG-10 HNG-14 Reader, 3128 File, 3128 

HNG-20 HHS-10 HSR-20 RAs 

Geometric and Roadside Design Acceptance Letter Number SS-39