November 7, 2003
Refer to: HSA-10/WZ-164
Ms. Kathy Rogalla
MDI Traffic Control Products
38271 West Twelve Mile Road
Farmington Hills, Michigan 48311-3041
Dear Ms. Rogalla:
This is in response to your letter of August 11, 2003, your prior email messages, and subsequent correspondence requesting Federal Highway Administration (FHWA) acceptance of variations to your company's portable sign stands as crashworthy traffic control devices for use in work zones on the National Highway System (NHS). Accompanying your correspondence were drawings and detailed descriptions of the stands and requested modifications. You requested that we find these 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."
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 devices follows:
MDI Model 5018 with breakaway features using Plywood signs
The MDI Breakaway Model 4818 was crash tested and accepted with 0.080 aluminum signs via FHWA Acceptance Letter WZ-69 on May 9, 2001. Based on information supplied by the crash test researchers, use of the Breakaway Model 4818 with 16 mm (5/8 inch) plywood was also considered acceptable. Your current request is for FHWA acceptance of 16 mm plywood signs Model 5018 sign with breakaway features. As the only difference between the 4818 and 5018 signs is the material the legs are fabricated from (Model 4818 stands have legs of 1.25 inch aluminum; Model 5018 stands have legs of 1.00 inch steel) we will consider this combination acceptable for use. Please note, however, that we consider any plywood sign mounted on an X-footprint stand at less than 5 feet to be in the "marginal" category.
MDI Model 4815-60 stand with roll-up, aluminum laminate, and Endurance signs.
The MDI Model 4815 stand, with sign mounted at 15 inches, was found acceptable in FHWA Acceptance Letter WZ-28. The configuration of the 4815-60 uses the same telescoping base as the 4815, but uses the crash-tested breakaway mast of the Model 4860 stand (supports a sign at 60 inches height and was accepted in WZ-69). The telescoping "footprint" of the proposed 4815-60 is smaller than the tested 4860 because the lightweight signs proposed for the 4815-60 are lighter than the plywood sign tested on the 4860 stand. The performance of the breakaway mast with the lightweight signs should be comparable to the version tested with the solid aluminum sign (4860).
Testing and Findings
Full-scale automobile testing was conducted on your company's comparable sign stands, with acceptable results. Based on the analysis detailed above, the devices described above and detailed in the enclosed drawings are acceptable for use on the NHS under the range of conditions that the comparable signs were tested, when proposed by a State.
Please note the following standard provisions that apply to FHWA letters of acceptance:
(Original Signed by John R. Baxter)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety