December 30, 2003
Refer to: HSA-10/WZ-167
Mr. Bill Fisher
Ply-Glo Safety Devices
RR # 2
Crossfield AB T0M 0S0 CANADA
Dear Mr. Fisher:
Thank you for your letter, received on December 17, 2003, requesting Federal Highway Administration (FHWA) acceptance of your company's illuminated road tubes as crashworthy traffic control devices for use in work zones on the National Highway System (NHS). Accompanying your letter were reports of informal crash testing you had conducted, dimensioned drawings of the devices, and a DVD containing video of the tests. 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:
The Ply-Glo Illuminated Safety Device is a low-density polyethylene road tube delineator mounted on a detachable rubber base. A light source is mounted in the base such that the light shining up through the tube illuminates it from within increasing nighttime visibility.
Roadtubes are nominally considered Category 1 devices by the FHWA, meaning they do not have to be individually tested. The addition of the lighting device to this product had the potential to significantly affect the crash performance, and resulted in the device requiring at least informal crash testing as a Category 2 device. Because the trajectory of the tube with its lighting device installed was our principal concern, informal vehicle testing was conducted on your company's device. Stand-alone examples of the devices were tested in numerous impacts, at various speeds, and with and without the lighting hardware. In every case the tube separated from the base. In those tests with the lighting device, no part of the device appeared to approach the windshield.
This crash-testing program used a van of a mass larger than the standard 820C test vehicle. There are significant constraints involved in using such a non-standard test vehicle, some of which are:
1. The potential vehicle velocity change must be considered insignificant.
2. The crush characteristics of an automobile bumper must not be expected to have a significant affect on the trajectory of the test article.
3. No part of the test article may have a trajectory that could propel it over the hood and into the windshield area of an 820C vehicle after impact.
In this case, testing of the Ply-Glo traffic safety marker device with the van was done within these constraints.
No part of the delineator or lighting device was projected up into the air or otherwise jeopardize the occupant compartment of the test vehicle. The results of the informal testing met FHWA requirements and, therefore, the devices 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.
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