Federal Highway Administration
400 Seventh St., S.W.
Washington, D.C. 20590
June 17, 2005
Refer to: HSA-10/WZ-211
Mr. Keith Callaway
MDI Traffic Control Products
38271 W. Twelve Mile Road
Farmington Hills, Michigan 48331-3041
Dear Mr. Callaway:
Thank you for your letter of April 13, 2005, requesting the Federal Highway Administration's (FHWA) acceptance of an aluminum rectangular sign with your company's 4860K Breakaway Stand as a crashworthy traffic control device for use in work zones on the National Highway System (NHS). Accompanying your letter drawings of the stand with the various signs in place. You requested that we find these devices acceptable for use on the NHS under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended Procedures for the Safety Performance Evaluation of Highway Features."
The FHWA guidance on crash testing of work zone traffic control devices is contained in two memoranda. The first, dated July 25, 1997, titled "INFORMATION: Identifying Acceptable Highway Safety Features," established four categories of work zone devices: Category I devices are those lightweight devices which are to be self-certified by the vendor, Category II devices are other lightweight devices which need individual crash testing but with reduced instrumentation, Category III devices are barriers and other fixed or heavy devices also needing crash testing with normal instrumentation, and Category IV devices are trailer mounted lighted signs, arrow panels, etc. for which crash testing requirements have not yet been established. The second guidance memorandum was issued on August 28, 1998, and is titled "INFORMATION: Crash Tested Work Zone Traffic Control Devices." This later memorandum lists devices that are acceptable under Categories I, II, and III.
A brief description of the device follows:
Model 4860K, with breakaway feature, tested with Aluminum panel and light:
(This stand was originally accepted in the FHWA acceptance letter WZ-69 dated May 9, 2001, and was the subject of Test MDI 6)
This stand is manufactured with two vertically mounted steel coil springs to support 1219 x 1219 x 2 mm (48 x 48 x 0.080 inch) aluminum signs. The four legs of the stand are 32 x 32 x 2.5 mm (1.25 x 1.25 x 0.10 inch) square 6061-T6 extruded aluminum tubing. The coil springs attach the 5 mm (0.19 inch) thick autophoretic coated steel base to the telescoping upright. The two-piece, upright, consisting of a 38 mm (1.50 inch)(bottom) and a 32 mm (1.25 inch)(top) square aluminum tube, supports the sign. The bottom upright has a scored "breakaway section" at 483 mm (19 inches) above grade when the stand is fully assembled. Rigid sign mounting brackets support the aluminum sign at top and bottom and a steel flag lock bracket is attached to the top upright supporting three hardwood dowel flags. A barricade light assembly, consisting of two a 6-volt battery batteries and a 178 mm (7 inch) polycarbonate lens, is mounted to the top upright above the flag bracket.
The overall height of the stand, with flags and light is 4115 mm (162 inches) and 3251 mm (128 inches) without the light and flags. The bottom of the sign is mounted 1524 mm (60 inches) above grade. The total weight of the sign stand is 31.6 kg (69.7 pounds) which includes the stand of 21.7 kg (47.7 pounds), the sign and flags of 8.4 kg (18.5 pounds) and the light of 1.6 kg (3.5 pounds) as tested in MDI 6.
Full-scale automobile testing was conducted on your company' devices. As reported in WZ-69 there was no damage to the windshield as the mast separated at the base and the sign and mast components rotated up and impacted the roof.
Your request is that the 4860K Breakaway stand be found acceptable with the following 48 x 60 (vertical) sign substrates listed with their approximate weights:
The tested sign was a 20-pound 48 x 48 aluminum sign. Sign substrates 1) through 4) are heavier than the tested system and should, after impact, allow the sign and mast to rotate about its center of gravity, moving up and away from the windshield. Substrates 5) and 6) may also go over the roof, but are light enough that there should be no significant damage to the windshield should the mast or sign impact it.
We concur in your assertion that the 4860K Breakaway sign stand with a 48 x 60 sign will perform in a similar manner to the tested system, therefore, the devices described above and detailed in the enclosed drawings are acceptable for use on the NHS under the range of conditions the 4860K Breakaway Stand was tested, when proposed by a State.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
/original signed by/
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety
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