U.S. Department

of Transportation 400 Seventh St., S.W.

Federal Highway Washington, D.C. 20590

Administration

Refer to: HSA-10/LS-51

Mr. Kash Kasturi

Senior Engineer, Structures and Transportation Group

Foster-Miller

350 Second Avenue

Waltham, MA 02451-1196

Dear Mr. Kasturi:

Thank you for your letter of September 20, 2001, requesting Federal Highway Administration (FHWA)

acceptance of your company’s “Composite Breakaway Coupling” for use with utility pole guy wires on

the National Highway System (NHS). Accompanying your letter was a report from the Southwest

Research Institute and videos of the crash tests. You requested that we find guy wires using your

company’s Safety Link 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 coupling 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.

The Foster-Miller coupling consists of a square fiberglass composite tube whose wall thickness was 1/4

inch and was 1.75 inches on a side. The device first tested (test FM-13) was 36 inches long and slotted

on each side. There were four slots, each 1/8 inch x 3 inches long equally spaced on two opposing

sides and three each 1/8 inch x 3 inches equally spaced on the remaining opposing sides. In test FM-16

the slot pattern was changed. Each side was only equipped with three slots and they were 1⁄2 inch wide

by 6 inches long and equally spaced at 3 inches apart along each side. Eight 0.06 inch notches were saw

cut into each slot. 

The ends of the tubes used in both tests were fitted with machined steel end plugs which were thrubolted with three each 3/8 inch bolts. The ends of the caps were machined to accept a standard 3/8

inch shackle. The coupling is shown in the enclosures for reference. 
2

Testing

Full-scale automobile testing was conducted on your company’s devices in test FM13. As the highspeed test proved that the breakaway concept worked as intended, a pendulum bogie was used for the

low-speed test. The masses of the test vehicle and the pendulum bogie were 820 kg.

Test # Impact Angle Speed Occup. Speed Delta V

FM13, 3-61 18.7 degrees 102.5 kmh 0.9 m/s 0.9 m/s

FM16, 3-60 20 degrees 35 kmh 0.2 m/s n/a

Speed: Actual impact speed of the test vehicle. Units are kilometers per hour.

Occup. Speed: The Occupant Impact Speed is the speed at which a theoretical front seat occupant will

contact the windshield. Units are meters per second.

Delta V: Speed change of the test vehicle before and after contacting test article. Units are meters per

second.

Findings

The test vehicle in test FM13 sustained damage to the front bumper and headlight/grille area. The hood

and both front fenders were deformed but repairable. All tires remained inflated during the impact

sequence. As mentioned above the low speed test was run with a pendulum bogie. Because the

coupling’s revised slot pattern in the low speed test would tend to improve the breakaway performance

of the coupling it was not deemed necessary to re-run the high speed test. Based on these tests the

Foster-Miller composite breakaway coupling is acceptable for use on the NHS when requested by a

State.

Please note the following standard provisions which apply to 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.

! 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 FHWA and NCHRP Report 350.

! To prevent misunderstanding by others, this letter of acceptance, designated as number LS-51

shall not be reproduced except in full. As this letter and the supporting documentation become

public information, it will be available for inspection at our office by interested parties.
3

! The Foster-Miller composite guy wire coupling is or will be a patented product and is 

considered "proprietary." The use of proprietary devices specified on Federal-aid projects,

except exempt, non-NHS projects: (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,

Michael L. Halladay 

Acting Program Manager, Safety 

Enclosure

FHWA:HSA-10:NArtimovich:tm:x61331:1/07/02

File: LS51FosterMillerFin.wpd

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

 N. Artimovich, HSA-10)


Sec. 635.411 Material or product selection. 

(a) Federal funds shall not participate, directly or indirectly, in payment for any premium or royalty on 

any patented or proprietary material, specification, or process specifically set forth in the plans and 

specifications for a project, unless: 

(1) Such patented or proprietary item is purchased or obtained through competitive bidding with equally 

suitable unpatented items; or 

(2) The State highway agency certifies either that such patented or proprietary item is essential for 

synchronization with existing highway facilities, or that no equally suitable alternate exists; or 

(3) Such patented or proprietary item is used for research or for a distinctive type of construction on 

relatively short sections of road for experimental purposes. 

(b) When there is available for purchase more than one nonpatented, nonproprietary material, 

semifinished or finished article or product that will fulfill the requirements for an item of work of a 

project and these available materials or products are judged to be of satisfactory quality and equally 

acceptable on the basis of engineering analysis and the anticipated prices for the related item(s) of work 

are estimated to be approximately the same, the PS&E for the project shall either contain or include by 

reference the specifications for each such material or product that is considered acceptable for 

incorporation in the work. If the State highway agency wishes to substitute some other acceptable 

material or product for the material or product designated by the successful bidder or bid as the lowest 

alternate, and such substitution results in an increase in costs, there will not be Federal-aid participation in 

any increase in costs. 

(c) A State highway agency may require a specific material or product when there are other acceptable 

materials and products, when such specific choice is approved by the Division Administrator as being in 

the public interest. When the Division Administrator's approval is not obtained, the item will be 

nonparticipating unless bidding procedures are used that establish the unit price of each acceptable 

alternative. In this case Federal-aid participation will be based on the lowest price so established. 

(d) Appendix A sets forth the FHWA requirements regarding (1) the specification of alternative types of 

culvert pipes, and (2) the number and types of such alternatives which must be set forth in the 

specifications for various types of drainage installations. 

(e) Reference in specifications and on plans to single trade name materials will not be approved on 

Federal-aid contracts. 

ENCLOSURE 2