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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-153A

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

August 22, 2011

In Reply Refer To:
HSST/B-153A

Jason D.C. Hubbell, President
The Atlanticum Bridge Corporation
P.O. Box 1644
Fort Walton Beach, Florida 32549

Dear Mr. Hubbell:

This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of a modification to a roadside safety system for use on the National Highway System (NHS).

Name of system: Nature Rail Quick Joint
Type of system: Aesthetic Guardrail System
Test Level: NCHRP Report 350 TL-2
Testing conducted by: TSR Engineering GmbH, Switzerland
ISO 17025 accreditation valid until March 2013
Date of request: December 22, 2010
Request initially acknowledged: December 22, 2010

You requested that we find this system acceptable for use on the NHS under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended Procedures for the Safety Performance Evaluation of Highway Features."

Decision:
The following device was found acceptable, with details provided below:

Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350 when tested prior to January 1, 2011, and the American Association of State Highway and Transportation Officials' Manual for Assessing Safety Hardware (MASH) if tested after that date.  The FHWA Memorandum "Identifying Acceptable Highway Safety Features" of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.

Description
The B-153 guardrail is comprised of steel components: c-channel posts; steel spacers and steel rails. Wood elements cover the steel post and rail components. The B-153 wood covering for steel posts are round. The wood coverings are connected to the steel post via a bolt that connects the steel post, the wood covering and the steel spacer together, as shown on the enclosed B-153 drawings.

The B-153 steel rail component is masked with a wood covering which is slotted and saddles the steel rail, as shown in the drawings. Three modifications differentiate the B-153 from the B-153A are: a) the horizontal 90 degree rotation of the steel c-channel post, b) change of the post's wood covering from round to rectangular in profile, and c) increase in the cross-section of the rail steel component at connections.

There are four structural differences between B-153 and B-153A.  The first is the rotation of the steel post.  The second, specifically with regard to the 4 meter post spacing configuration, is the addition of a 5mm thick steel rail component on the away-from-traffic side of the rail.  The third is the steel spacer.  The fourth is the configuration of the splice.  Collectively these structural changes have been shown, through testing to have reduced the guardrail system's maximum dynamic deflection.

The B-153 steel spacer consists of a bent steel plate.  The B-153A spacer is a 3/4 hexagonal shape welded to a steel plate.  The B-153A “honeycomb” spacer is stiffer than the B-153 spacer. The B-153 rail splice is made by overlapping the steel rail sections which doubles up on the overall thickness of the steel at the splice as compared to the rest of the rail.  The B-153A rail splice is a 3mm thick plate that is folded in half and saddles on top of the steel rail components of two sections of rail.  This means the overall thickness of steel at the splice of the B-153 has increased by 1mm in the 2m post spacing configuration and 6mm in the 4m post spacing configuration.

Improvement in dynamic deflection is seen when comparing the B-153 test results to the B-153A test results.  The B-153's 4m post spacing configuration had a maximum dynamic deflection with the heavy v ehicle test of 2.1m (approximately 6.9 feet).  The B-153A's 4m post spacing configuration under the same testing conditions had a maximum dynamic deflection of 1.4m, a one-third reduction in deflection.

Crash Testing

FHWA Acceptance Letter B-153, dated January 17, 2007, found the Nature Rail system acceptable for use on the NHS at NCHRP Report 350 Test Level 2.  Four full-scale crash tests of the modified Nature Rail were performed according to EN1317 norms. These tests are summarized below and the Test Data Summary Sheets are enclosed for reference.

EN-1317 Designation Test Lab Number Vehicle
model & weight
Impact Speed Angle of Impact Post Spacing Dynamic
Deflection
TB 32 PHG3 1991 Opel
3251 pounds
67.8 mph 20.5 degrees 2.0 m 4.6 feet
TB 11 PHG4 1993 Peugot
1804 pounds
61.2 mph 20.5 degrees 2.0 m 3.0 feet
TB 11 PHG6 1993 Peugot
1795 pounds
60.0 mph 20.0 degrees 4.0 m 3.9 feet
TB 32 PHG7 1994 Opel
3304 pounds
67.8 mph 20.0 degrees 4.0 m 6.2 feet

Findings
The occupant risk factors in each of the listed EN-1317 test were met.  While EN-1317 testing is ordinarily not accepted for use on the NHS, you are requesting FHWA acceptance of a modification to an existing system, and only to NCHRP Report 350 Test Level 2.  The Impact Severity of a TL-2 pickup truck test required under Report 350 (Test 2-11) is nominally 67.6 kJ. The Impact Severity of the EN-1317 TB 32 tests (PHG3 and PHG7) noted above was 88.78 kJ and 86.02 kJ respectively, which are significantly higher than the Report 350 TL-2 tests. We concur that these tests are adequate to establish equivalent performance of the modified barrier design.

The system described in the requests above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.

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

 

Sincerely yours,

/* Signature of Michael S. Griffith */

Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety

Enclosures

Page last modified on August 16, 2011.
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