1200 New Jersey Ave., S.E. 

Washington, DC 20590

August 23, 2007 

In Reply Refer To: 

HSSD/SS-152 

Mr. Raymond Kisiel 

Northwest Pipe Company 

6307 Toledo Street 

P.O. Box 2002 

Houston, TX 77252-2002 

Dear Mr. Kisiel: 

Thank you for your letter of June 1, 2007, requesting the Federal Highway Administration’s 

(FHWA) acceptance of your company’s 30 inch anchors used with perforated square steel tube 

(PSST) posts as crashworthy sign supports for use on the National Highway System (NHS). 

Accompanying your letter was a report from the Texas Transportation Institute of the crash tests 

conducted. You requested that we find your company’s PSST sign supports acceptable for use 

on the NHS under the provisions of the National Cooperative Highway Research Program 

(NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of 

Highway Features.” 

Introduction 

Testing of the device was in compliance with the guidelines contained in the NCHRP Report 

350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. 

Requirements for breakaway supports are those in the American Association of State Highway 

and Transportation Officials' Standard Specifications for Structural Supports for Highway Signs, 

Luminaires and Traffic Signals. 

Testing 

Bogie pendulum testing was recently conducted on your company’s various anchor lengths for 

PSST supports, ranging in length from 30 inches to 56 inches. The mass of the bogie pendulum 

was 820 kg. The tests were conducted at the typical 18 inch bumper height for small cars. 

Although pendulum tests are not routinely accepted for use with base bending or yielding 

supports, the crash behavior and post impact vehicle trajectory is fairly well known for PSST 

supports. Of the five tests conducted, the defining test was conducted on a 2-1/4 inch, 12 gauge 

PSST post inserted into a 2-1/2 inch by 30 inch, 12 gauge PSST anchor embedded 28 inches into 

standard soil. The summary of results from this test is enclosed. The post was inserted one foot 

into the anchor and secured in place with one 5/16 inch corner bolt and nut. A 48 by 36 inch by 

5/8 inch thick plywood sign panel was attached to the post at a height of 7 feet from ground 

level. Detailed drawings of the sign support assembly are enclosed. 
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Findings 

The pendulum bogie, traveling at a speed of 21.5 mph (35 km/hr), impacted the sign support at 

18 inches above ground level. Upon impact, the support yielded at the impact point, pulled out 

of the ground, and came to rest 63 feet downstream of the impact point. The total crush to the 

pendulum nose (surrogate bumper) was 3.6 inches. The pendulum bogie test impact displayed a 

low potential for intrusion into the occupant compartment, measured a maximum acceleration of 

-0.6 g’s, and a velocity change of -2.9 m/s. The measured velocity and acceleration changes 

were well within acceptable limits, and because the support pulled out of the ground there was 

no remaining stub to measure. The results of testing met the FHWA requirements and, therefore, 

the device described above and shown in the enclosed drawings for reference are acceptable for 

use as test level 3 devices on the NHS under the range of conditions tested, when proposed by a 

State. 

Additionally, you requested this PSST system to be considered acceptable for the following 

configurations: 

• A 2-1/4 inch, 14 gauge post inserted in a 2-1/2 inch by 30 inch, 12 gauge anchor. 

• A 2 inch, 12 gauge post inserted in a 2-1/4 inch by 30 inch, 12 gauge anchor. 

• A 2 inch, 14 gauge post inserted in a 2-1/4 inch by 30 inch, 12 gauge anchor. 

• A 1-3/4 inch, 12 gauge post inserted in a 2 inch by 30 inch, 12 gauge anchor. 

• A 1-3/4 inch, 14 gauge post inserted in a 2 inch by 30 inch, 12 gauge anchor. 

The additional requests listed above are acceptable based on the test conducted on the 2-1/4 inch 

12 gauge PSST post inserted into a 2-1/2 inch by 30 inch, 12 gauge PSST anchor embedded 

28 inches into standard soil. The additional configurations requested are slightly less rigid 

systems and are likely to yield in the same manner while producing similar or less severe impact 

results. This acceptance is based on the reported crash performance of your device and is not 

meant to address the limitations of testing or the systems’ installation, maintenance, or repair 

characteristics. 

Please note the following standard provisions that apply to the FHWA letters of acceptance: 

• This acceptance is limited to the crashworthiness characteristics of the devices and does not 

cover their structural features, nor conformity with the Manual on Uniform Traffic Control 

Devices. 

• Any changes that may adversely influence the crashworthiness of the device will require a 

new acceptance letter. 

• Should the FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the device being marketed is 

significantly different from the version that was crash tested, it reserves the right to modify or 

revoke its acceptance. 

• You will be expected to supply potential users with sufficient information on design and 

installation requirements to ensure proper performance. 
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• You will be expected to certify to potential users that the hardware furnished has essentially 

the same chemistry, mechanical properties, and geometry as that submitted for acceptance, 

and that they will meet the crashworthiness requirements of the FHWA and the NCHRP 

Report 350. 

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

SS-152 shall not be reproduced except in full. This letter, and the test documentation upon 

which this letter is based, is public information. All such letters and documentation may be 

reviewed at our office upon request. 

• The device is a patented product and considered proprietary. If 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 the 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. 

• This acceptance letter shall not be construed as authorization or consent by the FHWA to use, 

manufacture, or sell any patented device for which the applicant is not the patent holder. The 

acceptance letter is limited to the crashworthiness characteristics of the candidate device, and 

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 applicant. 

Sincerely yours, 

George E. Rice, Jr. 

Acting Director, Office of Safety Design 

Office of Safety 

Enclosures 

FHWA:HSSD:MLupes:tb:x66994:8/7/07 

File: s://directory folder/mlupes/SS152-NWP30inAnchor.doc 

cc: HSSD (Reader, HSA; Chron File, HSSD; M.Lupes, HSSD 

 M.McDonough, HSSD)