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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-194

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U.S. Department of Transportation
Federal Highway Administration

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

August 21, 2009

In Reply Refer To: HSSD/B-194

Mr. Robert Meline
Roadside Safety Research Group
California Department of Transportation
5900 Folsom Blvd
Sacramento, CA 95819

Dear Mr. Meline:

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

Name of system:California Type 90 Concrete Bridge Rail
Type of system:Steel Post and Beam mounted on Concrete Curb
Test Level:Test Level 4 (TL-4)
Testing conducted by:Roadside Safety Research Group, California Department of Transportation
Date of request:January 20, 2009

You requested that we find this system 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.”

Requirements
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features". FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The bridge rail is a steel post and beam system atop a concrete curb that has a reverse-slope of 5.2 degrees. This design raises the reaction point of impacting vehicles which reduces roll. The concrete curb is 550 mm (21 1/2 inches) high, 500 mm (19 1/2 inches) wide at the top, and 450 mm (17 3/4 inches) wide at the base. The top of the steel rail is 925 mm (36 1/2 inches) above the travel way. The steel rail consists of 254 x 102 x 6.4 mm (10 inch x 4 inch x 1/4 inch thick) tube steel welded to 178 x 127 x 7.9 mm (7 inch x 5 inch x 5/16 inch) tube steel posts spaced 3 m (10 feet) apart. Two 6-mm (1/4 inch) thick steel plates are welded to the backside of the rail and the back of each post to add stiffness to the post-rail connection. The posts are welded to a base plate that is rigidly attached to the concrete curb with anchor rods cast into the curb. See attached design drawings.

Crash Testing
The California Type 90 Concrete Bridge Rail was crash tested by Roadside Safety Research Group, California Department of Transportation. The barrier had some permanent damage. The vehicle lug nuts and rims caused gouging and spalling of the top of the concrete curb from just upstream of the initial impact point to where the rear tire lost contact with the rail, about 4.5 m downstream of the impact point. At posts 3 and 4 the spalling extended to the front edge of the post base plate. The gouging and spalling were superficial and not structural as evidenced by the lack of exposed reinforcement barsT. In addition, there was minor weld cracking at Post 3 (the post nearest the impact location) where the post was attached to the base plate. The welds were cracked approximately 6 mm on each side of all four corners, with a 0.05-mm gap at the crack locations. The center of the base plate was also bent upwards on the traffic and upstream sides, with the maximum deformation of 5 mm (1/5 inch) occurring on the traffic side. Additionally, the steel rail had a permanent lateral deflection of less than 15 mm (3/5 inches).

Findings
We concur that the California Type 90 Concrete Bridge Rail meets all barrier structural adequacy and vehicle trajectory criteria as outlined in NCHRP Report 350 and is acceptable for use on the NHS as a TL-4 barrier when allowed by the highway agency. Please note the following standard provisions that apply to FHWA letters of acceptance:

 

Sincerely yours,

Signature of David A. Nicol

David A. Nicol, P.E.
Director, Office of Safety Design
Office of Safety

Enclosures

Page last modified on June 24, 2011.
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