Refer to: HSA-10/SS-96

Mr. Jason Davenport
Utility Structural Systems
2201 N.Collins Street, Suite 240
Arlington, TX 76011

Dear Mr. Davenport:

This is in response to the May 11 letter from your company requesting Federal Highway Administration (FHWA) acceptance of your company's Poly-Set HD as foundation material for use with breakaway sign post systems on the National Highway System (NHS). Accompanying your letter was a video of the installation of a small sign post using your company's material and an April 30 letter from Mr. Roger Bligh of the Texas Transportation Institute (TTI) transmitting information on crash testing conducted for the State of Texas on a slip base sign support system using Poly-Set. The final test report was unavailable at the time. Subsequently, on August 21 you met with Mr. Nicholas Artimovich of my staff to discuss your product and possible applications including breakaway wood posts.

Introduction

Requirements for breakaway supports are those in the American Association of State Highway and Transportation Officials' (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. Crash testing of breakaway supports is covered in the National Cooperative Highway Research Program (NCHRP) Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features.

The Poly-Set HD is an engineered backfill that is a specially modified, high density, polyurethane product. It expands up to 8.5 times its original volume by transforming the two-part liquid components into a solid foundation material in minutes. Information on compressive strength, density, and tensile properties of the tested material were provided for our files.

Full-scale automobile testing was conducted at TTI on a single support omni-directional slip base installation with a 72.2 mm (3-inch) diameter schedule 40 steel pipe support. Two tests were run, at 35 km/h and at 100 km/h using Poly-Set HD foam backfill foundation material. The size of the foundation was 305 mm diameter by 1060 mm deep (12 inches x 42 inches). Since slip base sign supports depend upon rigid foundations to perform as intended, expanding foam backfill materials need to be strong enough to resist crushing in order to provide this acceptable foundation.

The low- and high-speed crash tests both resulted in occupant impact speeds of 1.1 m/s, well under the 5.0 m/s maximum as specified in NCHRP Report 350. The test articles did not show any potential for penetrating the passenger compartment, and there was no observable distress or

movement of the foam foundation material. Based on these tests the State of Texas approved use of your company's product. We also concur that Poly-Set HD is an acceptable foundation material for breakaway small sign support systems such as omni-directional three-bolt slip bases. Therefore, Poly-Set HD is acceptable for use when backfilling certain breakaway small sign supports mounted in standard soil conditions on the NHS under the range of conditions tested, when proposed by a State. The acceptable sign support systems are the tested omni-directional slip base and the following wood post systems:

*Number of such posts permitted within a 2.1 m (7-foot span.)

** Holes are to be drilled into the long side of the post (the side that is parallel to traffic) and at heights of 4 inches and 18 inches above the ground.

Please note the following standard provisions which apply to FHWA letters of acceptance: