Refer to: HSA-10/WZ-100 Amendment #2
Mr. William E. Korman, Jr.
3029 Lincoln Avenue
Richmond, Virginia 23228
Dear Mr. Korman:
This is in response to your letters of March 19 and April 8, 2003, requesting Federal Highway Administration (FHWA) acceptance of a modification to your company's crashworthy portable sign stand for use in work zones on the National Highway System (NHS). You requested that we find the SS548E and SS548AE sign stands, when modified with telescopic legs, 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 were those lightweight devices which could be self-certified by the vendor, Category II devices were other lightweight devices which needed individual crash testing, Category III devices were barriers and other fixed or massive devices also needing crash testing, and Category IV devices were trailer mounted lighted signs, arrow panels, etc. 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:
The SS548E and SS548AE stands hold 48x48 inch roll-up signs at a height of 60 inches. The legs are 1.25 inch square, 16 gage steel tubing and are 48 inches long. The base of the mast is 27 inches long of 1.25 inch square steel tubing, 14 gage wall thickness with an extension spring arrangement. The upper portion of the telescoping mast is 72 inches long 1 inch square tubing, also 16 gage steel. It extends to the middle of the sign where it holds the sign mounting bracket.
The modification you requested was to substitute telescoping legs (29 inches plus 24 inches extension) for the rigid legs. Based upon crash testing that led to FHWA Acceptance Letters WZ-21, WZ-29, and WZ-100, it can be expected that the modification will not have an adverse effect on the safety performance of the stands. Your letter of April 8, 2003, requested that the model numbers of these two stands be modified with the letters "TL" to indicate the use of telescopic legs.
We concur that the modification of the legs of the crashworthy sign stands SS548E and SS548AE to include telescoping legs, to be designated SS548ETL and SS548AETL, and as described above and detailed in the enclosed drawings are acceptable for use on the NHS under the range of conditions tested, when proposed by a State.
We also concur with your request to modify your other crashworthy X-footprint sign stands by making the legs telescopic instead of a one-piece design, as needed. The overall length of each leg should be similar to that of the one-piece legs.
Please note the following standard provisions that apply to FHWA letters of acceptance:
Michael S. Griffith
Acting Director, Office of Safety Design
Office of Safety