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U.S. Department of Transportation

Federal Highway Administration

400 Seventh St., S.W.
Washington, D.C. 20590

January 17, 2007

In Reply Refer To: HSSD/B-153

Mr. David Hubbell
P.O. Box 600
Saranac Lake, NY 12983

Dear Mr. Hubbell:

Thank you for your letter of June 26, 2007, requesting the Federal Highway Administration (FHWA) acceptance of your company’s NatureRailTM aesthetic weak-post barrier for use on the National Highway System (NHS). Accompanying your letter were reports of crash testing conducted by the French testing laboratory LEIR and video of the tests. You requested that we find this device acceptable for use on the NHS use at test level 2 (TL-2) under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features” when compared to the successfully tested TL-3 aesthetic “Ironwood” barrier covered under the FHWA acceptance letters B-56 (dated June 18, 1999), and B-56A (May 11, 2000) and B-56B (September 5, 2003). You supplied additional information comparing the NatureRailTM to another tested system on December 19, 2006.

Introduction
The FHWA guidance on crash testing of roadside safety hardware is contained in a memorandum dated July 25, 1997, titled “INFORMATION: Identifying Acceptable Highway Safety Features.”

Testing was conducted on three NatureRailTM configurations:

Brief descriptions of the devices, taken from the LEIR test reports, follow:

NatureRail™ 519
The system tested was a protective system made of wood and metal comprising cylindrical posts averaging 180 mm in diameter and 1,980 mm high as a crash barrier. Flat 100 x 5 metal rails 4,650 mm in length were used as interior reinforcement. The crash barriers were screwed tightly to C100 x 50 x 25 x 5 posts (1,500 mm high). The posts were paneled with round timber (averaging 160 mm in diameter and 670 mm high) and rammed into the ground 2 metres apart. The connection between the crash barrier and the posts was secured using metal spacers (100 x 50 x 650). The connection between the spacers, paneling and posts was ensured by a class 4.6 screw, a H, M12 nut and an M12 washer.

NatureRail™ 593
The system tested was a protective system made of wood and metal comprising cylindrical posts averaging 180 mm in diameter and 1,980 mm high as a crash barrier. Flat 100 x 5 metal rails 4,650 mm in length were used as interior reinforcement. The crash barriers were screwed tightly to C100 x 50 x 25 x 5 posts (2,000 mm high). The posts were paneled with round timber (averaging 160 mm in diameter and 670 mm high) and rammed into the ground 4 metres apart. In order to form an even more rigid connection between the round wood posts and reinforcement panels, an additional U100 metal reinforcement element 800 mm in length was screwed behind the crash barrier in the spaces between posts. The connection between the crash barrier and the posts was secured using metal spacers (100 x 50 x 650). The connection between the crash barrier, spacers and metal reinforcing elements was screwed using 4 class 4.6 TRCC M16 x 200 screws, 4 H, M16 nuts and 4 M16 washers. The connection between the spacers, paneling and posts was ensured by a H, M12 x 60 class 4.6 screw, a H, M12 nut and an M12 washer.

NatureRail™ 744
The device tested is a wood and steel safety barrier with obstacle protection. It consists of C100 posts, 2.00 m in length, beaten into the ground every 1.00 m. The posts are trimmed with logs. A set of pre-assembled rails consisting of two logs – RH and LH (Ø 180 mm, length 1,980 mm) secured to a flat metal reinforcement (100x, length : 4,650 mm). The wood/metal rails are assembled together by overlapping. The pre-assembled assemblies are reinforced by a metal rail C100 x 50 x 25 x 5, length : 5,998 mm, placed at the rear of the logs. The metal rail is secured to the posts by means of a connection/spacers part. The rails are mounted by means of 4 special round-head bolts, quality 8.8, M16 x 170, and 4 Ø 18 washers (ext. Ø:40, thk.: 5 mm) and threaded plates M16 200 x 80, thk.:12 mm. This assembly is secured to a connection piece/spacer by means of 4 M16 x 30 hex screws, four 18 x 5 washers and 4 M16 hex nuts, and two threaded plates M16 200 x 80 x 12. The connection piece/spacer is secured to the post by means of hex head 12 x 60 screws, a Ø 14 washer and a M12 hex bolt. The post's wood trim is placed between the metal support and the connection piece/spacer. The connection between the rear metal reinforcements is made by means of sleeves C85 x 35 x 16, thk.: 4 mm, length 240 mm and 4 hex head bolts, M12 x 60, 4 washers and 4 nuts.

Drawings of these barriers are enclosed for reference. Also enclosed are drawings that show the significant differences between the TL-3 Ironwood barrier and the TL-2 NatureRail™ designs.

Testing
Full-scale automobile testing was conducted by the Inrets Road Equipment Test Laboratory to EN 1317, N-2 standards.

The CEN tests are summarized in the table below:

Findings
The results of the CEN testing indicate that the three tested NatureRail™ configurations perform in a manner at least comparable to

Test/Product
Number
Impact
Speed
Impact
Angle
Vehicle Mass Deflection
Max. Dynamic Permanent
519 113.3 km/hr 20.0 deg 1430 kg 1.5 m 0.56 m
593 112.3 km/hr 20.0 deg 1429 kg 2.1 m 0.92 m
744 116.4 km/hr 20.0 deg 1451 kg 0.9 m 0.8 m

the NCHRP Report 350 TL-3 accepted Ironwood barrier. As you requested the FHWA acceptance to Report 350 TL-2 criteria we concur that the devices described in the various requests above and detailed in the enclosed drawings are acceptable for use on the NHS under TL-2 conditions, when proposed by a highway agency. Acceptance is limited to TL-2 conditions as testing with the 2000P pick up truck has not been conducted.

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

 

Sincerely yours,

Signature of John R. Baxter

John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety

Enclosures


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