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US Department of Transportation

Federal Highway Administration

Subject: ACTION: Requests for Public Interest Findings for 3M Prismatic Retroreflective Sign Sheeting Materials

Date: December 5, 2007

From: Jeffrey A. Lindley, Associate Administrator for Safety

In Reply Refer To: HSA

To: Division Administrators

As many of you are already aware, earlier this summer 15 Division offices received requests for public interest findings (PIFs) from their respective State Departments of Transportation for a new prismatic retroreflective sign sheeting material manufactured by 3M called Diamond Grade Cubed (DG3). These PIF requests were submitted pursuant to 23 CFR 635.411 (c), which allows Division Administrators to approve the use of a proprietary product upon request by a State when it is in the public interest to do so. In these PIF requests, each State asserts that DG3 offers superior performance primarily because of its higher brightness (luminance level) in many situations. The States have requested public interest findings allowing DG3 to be specified on a sole source basis on Federal-aid projects for all guide signs, chevrons, markers and delineators for a period of three years. A detailed technical justification outlining performance advantages for DG3 over other commercially available sign sheeting products was included with each request.

Due to the unique nature of this situation – i.e. multiple, identical requests for PIFs using a common set of technical documentation – we requested that the Divisions forward these requests to Headquarters so that our agency response would be consistent. Upon receiving these requests, we performed an evaluation involving FHWA technical experts in sign retroreflectivity issues, as well as other staff in the Offices of Safety, Infrastructure, Operations, Research & Technology, and the Chief Counsel’s office. A detailed review of the technical justification of safety benefits has been performed, as well as a preliminary evaluation of the claimed benefits versus the higher cost for DG3 material, including consideration of the potential impact that approving the PIFs as requested could have on the marketplace for traffic sign sheeting products and traffic sign fabrication in the States making PIF requests.

Based on our review, we have determined that additional information is needed before a full approval of the PIFs could be granted. However, we believe that an approval on a more limited basis for experimental purposes under 23 CFR 635.411(a)(3) is appropriate as outlined below. Our review confirms some of the claimed benefits of DG3. However, it also raises questions about the magnitude and significance of others, as well as noting that many of the estimated benefits are based on computer modeling instead of experimental data. Our evaluation also raises concerns about the possibility that use of DG3 on chevrons in rural areas could create disability glare and recommends further study of the potential adverse impacts of this application. Accordingly, since we feel that more information is needed, a broad finding that the use of DG3 is in the public interest pursuant to 23 CFR 635.411(c) is not warranted at this time.

Under 23 CFR 635.411(a)(3), States are permitted to experiment with new products on a more limited basis in order to produce experimental data to better understand performance characteristics and perhaps support more widespread specification of a product. Such a request was not made regarding DG3. We encourage any interested State, including the 15 States that submitted the PIF requests, to consider such experimentation on as extensive a level as they deem appropriate as a means to develop an adequate justification for a full PIF. In order to support production of relevant and reliable data, we have prepared the attached guidance on how such experimentation should be pursued. Because States may find the experimental approach required to produce relevant data to be costly and complicated if pursued on a State by State basis, we encourage States to pool resources to support experimental evaluations. FHWA is willing to help facilitate this process, if so desired and requested by the States. States interested in specifying DG3 on a more widespread than experimental basis continue to have the option to do so as a non-participating item, as outlined in the existing regulations.

As a final note, the decision to make a national determination of FHWA’s position on the requests for PIFs in this case is due to the unique circumstances surrounding this situation – namely, multiple and simultaneous requests regarding a single product. The consolidated review used in this case is not intended to set a precedent for action in handling future requests. However, given the determination made regarding the need for additional justification for PIFs involving DG3, ongoing review of that product will continue to be handled by Headquarters. We are also currently reviewing options to ensure that our processes to review PIF requests are effective in promoting innovation and advancing the state of the practice in the highway industry.

For further information on the technical aspects of this issue, please contact Messrs. Carl Andersen in the Office of Safety Research at (202) 493-3366 or Greg Schertz, Retroreflectivity Team Leader, at (720) 963-3764.


cc: Director of Field Services
Federal Lands Highway Division Engineers
Resource Centers Directors
Chief Counsel
Associate Administrator for Infrastructure
Associate Administrator for Operations
Associate Administrator for Research Development, and Technology
Page last modified on October 28, 2016
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