Refer to: HSA-10/WZ-156
Mr. Paul Lang
Lang Products International
1919 4th St. N.E.
Minneapolis, Minnesota 55418
Dear Mr. Lang:
This is in response to your letter of April 15, 2003, requesting Federal Highway Administration (FHWA) acceptance of your company's portable sign stand, with modifications, as a crashworthy traffic control device for use in work zones on the National Highway System (NHS). Your stand, the LTT-1 portable sign support frame, was initially found acceptable by the FHWA on August 13, 2002, (Acceptance Letter WZ-126.) You requested that we find this stand 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" with lightweight lights and 0.100 inch thick aluminum sign substrates.
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.
The LTT-1 portable sign consists of a 1220 x 1220 mm (48x48 inch) diamond shaped 12.7 mm (½ inch) thick MDO plywood sign attached to 44.5 mm square, 2.7 mm thick (1 ¾ inches x 12 ga) perforated square steel tube uprights supported by 50.8 mm square, 3.0 mm thick (2 inches x 11 ga) steel tube removable arched legs. The uprights are secured onto the arched legs by a 22 inch x 1.5 inch x 1.5 inch x 3/16 inch receiver stud that fits inside the lower portion of the uprights. This stud is permanently welded onto the arched leg in a perpendicular orientation. All tubing is ASTM A500 Grade B steel. The fasteners are 76.2 mm (3 inch) long 7.9 mm (5/16 inch) grade 5 bolts secured by nylon insert lock nuts. The height of the bottom tip of the sign was a nominal 304.8 mm (12 inches) above ground level.
Your current request is for the following modifications:
The sign stand as crash tested and as described above, with the substitution of 2.54 mm (0.100-inch) thick aluminum for the 12.7 mm (½ inch) thick MDO plywood sign, and the use of a lightweight warning light, not to exceed 3.3 pounds.
Crash testing conducted by the Midwest Roadside Safety Facility (MwRSF) on a similar rigid-frame generic portable sign stand supports your requests. The stand tested by MwRSF supported an aluminum sign panel of 0.100-inch thickness, and also carried a lightweight warning light. It was found acceptable in our Acceptance Letter WZ-133 dated November 26, 2002. The performance of the MwRSF stand was similar to that of your stand - the stands in both tests were knocked aside by the vehicle and showed little, if any, potential for causing significant damage to the windshield.
Because of the similarity in performance between the LTT-1 and the MwRSF generic stand, and the fact that the MwRSF stand included the sign substrate and warning light you requested for your stand, we concur that the modifications you have requested to the LTT-1 stand will be acceptable for use 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:
Michael S. Griffith
Acting Director, Office of Safety Design
Office of Safety