U.S. Department 

Of Transportation 

Federal Highway 

Administration

400 Seventh St., S.W. 

Washington, D.C. 20590 

August 3, 1989 

Refer to: HNG-14/SS-12 

Mr. John Freeman 

President, HwyCom 

P.O. Box 2119 

Big Spring, Texas 79721-2119 

Dear Mr. Freeman: 

This is in response to your July 21, 1989 letter to the Federal Highway Administration 

(FHWA) requesting acceptance of your company’s double fiberglass small sign supports 

for use on Federal-aid highway projects. Tests were conducted to assess the compliance 

of these supports with FHWA requirements, which cite Section 7 of the 1985 American 

Association of State Highway and Transportation Officials (AASHTO) Standard 

Specifications for Structural Supports for Highway Signs, Luminaires and Traffic 

Signals. In support of this request your included two crash test reports from Texas 

Transportation Institute, and referred to your earlier submission which included 

manufacturing and installation details for a like single post support which received 

FHWA acceptance on May 11, 1989. 

Both full-scale crash tests used the same 1,800 pound Honda Civic. The test installation, 

shown in Enclosure 1 consisted of a 4-foot by 6-foot sign panel mounted on two 3-inch 

diameter fiberglass support posts spaced 38 inches center-to-center. The posts were 

inserted into 27-inch long steel support tubes for a distance of 12 inches and secured with 

self-tapping screws. The support tubes, flattened for approximately half their length, had 

been driven into NCHRP “strong” soil. Other test details and results are shown below: 

Test # Impact 

Speed 

(mph) 

Vehicle 

Delta V 

(fps) 

Vehicle 

Longitudinal 

Accelerations 

(g’s) 

Occupant Impact 

Velocity 

Longitudinal (fps)

Occupant 

Ridedown 

Accelerations 

longitudinal (g’s)

0366-3 20.2 23.8 -3.8 15.0 -4.8 

0366-4 59.7 4.1 -1.7 * * 

*No theoretical occupant contact with vehicle interior during evaluation period of event. 
In the low speed test the posts did not disengage from the support tubes as the vehicle 

rode over the installation. The posts were pulled entirely out of the flush-mounted 

support tubes during the high-speed test. In the low speed test, the occupant impact 

velocity did not exceed 16.0 fps, while the high-speed test did not result in an occupant 

impact with the interior of the vehicle. 

These results meet the change in velocity and stub height requirements adopted by the 

FHWA. Therefore, your company’s dual post sign support described above and in the 

enclosures is acceptable for use on Federal-aid highway projects, within the range of 

conditions tested, if proposed by a State. We note this system was only tested in the 

strong (S-1) soil described in NCHRP Report 230. Usually we would suggest that 

breakaway supports be tested in weak (S-2) soil. However, with the short foundation 

embedment specified for your support, we consider this additional testing unnecessary. 

On the other hand users should be cautioned not to use the support in weak soil, if to do 

so, requires an increase in foundation embedment or other revision in the foundation, 

unless the revised design is tested. 

This acceptance is limited to breakaway characteristics of the system and does not cover 

is 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 HwyCom that 

the hardware furnished has essentially the same chemistry, mechanical properties, and 

geometry as that used in the tests, and that it will meet the FHWA change in velocity 

requirements. 

Since the HwyCom post and base system is a proprietary item, to be used in a Federal-aid 

project they: (a) it must be supplied through competitive bidding with equally suitable 

unpatented items; (b) the State highway agency certifies that it is essential for 

synchronization with existing highway facilities or that no equally suitable alternate 

exists; or (c) it is 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, have 

previously been given to representatives of HwyCom. However, for your convenience, 

another copy is enclosed. 

 Sincerely yours, 

 L. A. Staron, Chief 

 Federal-Aid and Design Division 

Enclosures