October 29, 1992
Refer to: HNG-14/SS-33
Mr. Tauhid Husain
Transpo Industries, Inc.
20 Jones Street
New Rochelle, New York 10801-6024
Dear Mr. Husain:
Thank you for your October 12 letter to Mr. Nicholas Artimovich requesting Federal Highway Administration's (FHWA) acceptance of your company's model 201C and 301C Pole-Safe couplings as meeting the breakaway requirements of 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. Transmitted with your letter were drawings of Transpo's previously accepted 201 and 301 Pole-Safe couplings, drawings of the new 201C and 301C models, and results of static tests performed on the new couplings to demonstrate their reduced transverse resistance.
The new couplings are similar to Transpo's model 201 and 301 Pole-Safe couplings except that they are designed for use with call box supports and provide a considerably reduced transverse resistance as well as a much lower tensile load carrying capability. The reduction in shear resistance (and tensile strength) result from reducing the length of engagement of the top stud in the aluminum casting. The while nylon coating on the new 201C and 301C models is the only external distinction between them and the higher capacity black-coated 201 and 301 models.
Based upon our review of the data you supplied, we believe that the model 201C and 301C couplings will meet breakaway requirements at least as well as do models 201 and 301. Therefore, your company's model 201C and 301C pole-Safe couplings described above and shown on the enclosed drawings are acceptable for use on Federal-aid highway projects for aluminum tube callbox supports [(280-mm (11-inch) bolt circle, 4.8-mm (0.188-inch) wall thickness] if proposed by a State.
Our acceptance is limited to breakaway characteristics of the couplings and does not cover their 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 Transpo Industries, Inc., that the couplings furnished will meet the FHWA change in velocity requirements and have essentially the same composition, mechanical properties, and geometry as those used in the certification tests of the model 201 and 301 couplings, except for the modifications to produce the model 201C and 301C couplings.
Pole-Safe couplings are proprietary. Thus, to be used in a Federal-aid highway project (a) they must be supplied through competitive bidding with equally suitable unpatented items; (b) the State 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 was provided with earlier correspondence.
Lawrence A. Staron, Chief
Federal-Aid and Design Division
Geometric and Roadside Design Acceptance Letter Number SS-33