October 22, 2002

Refer to: HSA-10/SS-108

Mr. Jack F. Glen, Jr.
Glenncast Inc.
4401 Acworth Industrial Drive
Acworth, Georgia 30101

Dear Mr. Glen:

Thank you for your letter of March 12 and facsimile transmission of July 18 requesting Federal Highway Administration (FHWA) acceptance of your company's aluminum sign poles with decorative castings at the base as breakaway sign support systems for use on the National Highway System (NHS). Accompanying your letter was a report from the Southwest Research Institute and videos of the pendulum tests. You requested that we find the combination STOP sign and street name sign devices 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." You also provided additional drawings per our request on September 25.


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' Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.

The sign systems as tested can be described as a stop sign and street name sign mounted on an aluminum pole with a decorative casting at the base. The tested support poles ranged from 14.3 ft to 15.8 ft in length. The poles were embedded in NCHRP Report 350 Standard (strong) soil. The 32-inch octagonal shaped, cast aluminum stop sign blank was mounted 7 ft from the bottom of the sign to grade in all cases. Two street name sign frames with blank fillers were mounted at 90 degrees to each other near the top of the pole. Five variations were crash tested using the 820 kg bogie. These variations are:

A. The post was a 4" x 4" x 0.156" square aluminum tube with a 5" x 4½" x 0.159" decorative channel at the base. The 4" x 4" tube was embedded directly into a 36-inch deep concrete foundation that had a diameter of 8 inches.

B. The design tested in "A" was modified with the addition of an aluminum plate butt welded on the bottom. This plate was 4½" x 4½"x ¼" thick with a 4" x

4" x 0.156" thick wall square tube butt welded to it.

C. Post "A" is a round steel post with an outside diameter of 2.375 inches and a wall thickness of 0.125 inches. Post "B" has an OD of 2.875 inches and a 0.19 inch wall thickness. The decorative base has a 4¾ inch OD at the top and 7½ inches at the bottom.

D. The design tested in "C" was modified by welding a 6½ inch OD x 3/8 inch thick plate to the bottom of the decorative base. A 2.375 inch OD x 0.125 inch wall aluminum pipe is welded to this plate.

E. The cast aluminum post is 4½ x 4½inches x 3/8 inches thick, with a 4¼ x 4 ¼ inch x ¼ inch thick plate welded on the bottom. A 4 inch OD x ¼inch wall pipe is butt welded to this plate.


Pendulum testing was conducted on your company's devices. The mass of the pendulum bogie was 820 kg in all tests. It was equipped with a 10-stage crushable honeycomb nose section. The complete signposts and breakaway castings as tested are shown in the Enclosures.

Test # NCHRP 350 Test # Speed Test article description Velocity change


3-60 35 km/hr

4x4" x 0.156" square aluminum tube. 5 x 4 1/2" decorative channel at base

1.3 m/s



100 km/hr

0.73 m/s



35 km/hr

4x4" x 0.156" square al. tube.

5 x 4 1/2" decorative channel at base. Al. Plate & pipe butt welded on bottom

0.70 m/s



100 km/hr

0.65 m/s



35 km/hr

2.375" x 0.125" round al. tube. 2.875" x 0.19 " round al. tube. Decorative base at bottom.

0.85 m/s



100 km/hr

0.57 m/s



35 km/hr

2.375" x 0.125" round al. tube. 2.875" x 0.19 " round al. tube. Decorative base at bottom, with plate and al. pipe welded to bottom.

0.49 m/s



100 km/hr

0.59 m/s



35 km/hr

Cast al. post 4½ x 4½ x 3/8" with a 4¼ x 4 ¼ plate welded to the bottom, and a 4" OD pipe welded below.

1.08 m/s



100 km/hr

1.88 m/s

Note: The support used in test "A" failed due to excessive stub height. No drawing of this design is included with this letter.


Velocity changes for the low-speed pendulum tests and the high-speed extrapolations were all within acceptable limits. All supports fractured at the ground line with the exception of Test A. In that test the fracture occurred at the top of the decorative collar, approximately 24 inches above the ground. The remaining post stub bent over in the soil, but remained well in excess of 4 inches. In light of the fact that you modified the design and retested it (Test B), and that this modified design both broke away cleanly at the groundline leaving no stub and resulted in lower velocity change, we find the unmodified version unacceptable.

Except as noted above the results of testing met the FHWA requirements and, therefore, the devices described above which were tested in impacts B, C, D, and E, and which are 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 FHWA letters of acceptance:

Sincerely yours,


Carol H. Jacoby,P.E.
Director, Office of Safety Design