February 9, 2006 400 Seventh St., S.W. 

Washington, D.C. 20590

In Reply Refer To: 

HSA-10/SS-132 

 

 

 Mr. Mark T. Salman, President 

 Sign Support Systems 

 P.O. Box 8041 

 Greensboro, NC 27419 

Dear Mr. Salman: 

Thank you for your letter of November 28, 2005, requesting Federal Highway Administration 

(FHWA) acceptance of a new model of your company’s Break Out Coupler for perforated 

square steel tubes as a breakaway sign support system for use on the National Highway System 

(NHS). Accompanying your letter was a report from the Texas Transportation Institute and 

videos of the crash tests. You requested that we find the new Break-Out Coupler acceptable 

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

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

Highway Features.” 

Introduction 

Testing of the supports 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' (AASHTO) Standard Specifications for Structural Supports for 

Highway Signs, Luminaires and Traffic Signals. 

The Break-Out Coupler is a cast-iron (ASTM A536 65-45-12 alloy) coupling with a shear 

section machined to a pre-set diameter to ensure breakaway performance of up to a maximum 

of 90 percent of the yield strength of the post it is used with. It was originally found acceptable 

in our letter SS-98 dated August 29, 2001, with U-channel posts and 2-inch perforated square 

steel tube (PSST) sign supports. The new version you have recently tested is designed for 

2 1⁄2 inch PSST supports. The cast neck of this model is subsequently machined with a groove 

that yields a final diameter of 1.900 inches. 

The sign support was 2 1⁄2 inch x 2 1⁄2 inch North West Pipe PSST with 12 gage fins (soil 

anchor). The 48x48x5/8 inch plywood sign panel was attached using 3/8 inch x 4-inch bolts 

6 inches from the top and bottom of the sign panel. The two-piece Break-Out casting was held 

 
2

together with 1/2 inch x 3 inch grade 8 flange bolt. The PSST support was secured into the 

Break Out casting with two 5/16 x 4 inch grade 5 hex-head bolts. 

Testing 

Pendulum bogie testing was conducted on your company’s devices. The mass of the bogie test 

vehicle was 839 kg in all tests. Two similar tests were run in the NCHRP Report 350 Standard 

Soil to verify the consistent performance of the Break Out Coupler. Both tests included the 

installation of a soil anchor just below the surface. A plywood sign panel was mounted to the 

impact face of the PSST at a height of 7 feet to the bottom. The complete devices as tested are 

shown in the enclosures. 

Test # NCHRP 350 Impact Speed Version Delta V Est. 60 mph Delta V 

SKD-P1 Test 3-60 35.0 km/hr Soil Plate 1.8 m/s 0.7 m/s 

SKD-P2 Test 3-60 35.1 km/hr Soil plate 1.5 m/s 0.7 m/s 

Occupant Impact Speed: Speed at which a theoretical front seat occupant will contact the 

windshield. In these two tests the device did not slow the vehicle enough to result in an 

occupant impact, i.e. “no contact.” 

Delta V: Speed change of the test vehicle. In meters per second. 

Est. 60 mph Delta V: Delta V of a theoretical high-speed test estimated using data from the 

pendulum test. 

Findings 

Velocity changes were all within acceptable limits, and the only stub remaining was flush with 

the level of the surrounding soil. The anchor moved 1.1 inches in the soil during test SKD-P1 

and moved 0.24 inches during test SKD-P2. The results of testing met the FHWA 

requirements and, therefore, the devices 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. 

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

• Our 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. 
3

• The Break Out Coupler is a patented device and is considered "proprietary.” When 

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

• 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-132 shall not be reproduced except in full. As this letter and the supporting 

documentation which support it become public information, it will be available for 

inspection at our office by interested parties. 

• 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, 

 

/original signed by/ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

Enclosures 

FHWA:HSA-10:NArtimovich:tb:x61331:2/2/06 

File: h://directory folder/artimovich/SS132-BreakOutFIN.doc 

cc: HSA-10 (Reader, HSA-1; Chron File, HSA-10; 

 N.Artimovich, HSA-10)