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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-42B

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U.S. Department of Transportation
Federal Highway Administration

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

July 17, 2009

In Reply Refer To:
HSSD/B-42B

Mr. Michael Budd
Rockingham Precast
P.O. Box 1347
Harrisonburg, VA 22801

Dear Mr. Budd:

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

Name of system: 12-Foot T-LOC F-Shape Portable Concrete Barrier
Type of system: Temporary concrete barrier
Test Level: AASHTO Manual for Assessing Safety Hardware (MASH) Test Level-3
Testing conducted by: Texas Transportation Institute (TTI) on May 5, 2009
Date of request: February 10, 2009
Initial response by email sent February 23, 2009

You subsequently requested that we formally find this device acceptable for use on the NHS under the provisions of the AASHTO Manual for Assessing Safety Hardware (MASH) Test Level-3 (TL-3).

Requirements
Roadside safety devices should meet the guidelines contained in the AASHTO Manual for Assessing Safety Hardware (MASH). The FHWA Memorandum "ACTION: Identifying Acceptable Highway Safety Features" of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The Rockingham Precast T-LOC barrier was originally accepted on October 20, 1997, in our Acceptance Letter B-42. The barrier tested was composed of 32-inch high, 12-foot long concrete F-Shape segments using a connection detail specifying 32-inch long slotted tube (4 inches × 4 inches × ½ inches) and mating fabricating 'T' made of ½-inch thick steel.

Your present request is for formal acceptance of 32-inch high, 12-foot long concrete F-Shape barrier segments using a connection detail specifying 12-inch long slotted tube connection (HSS4 × 4 × 1/2) anchored to the end of barrier segments using four #6 dowel bars 24 inches in length welded to the sides of the slotted tube (two on each side). The width of the slot in the tube was 1 inch. The interlocking mating "T" connection was fabricated using ½-inch thick steel plate. The width and length of the "T" connection was 2 inches and 12 inches respectively. The "T" connection was anchored to the ends of the barrier units using three #6 bars, 36 inches in length, and welded to the "T" connection steel. These bars, along with the bars welded to the slotted tube connection, were cast within the barrier concrete for each unit. Both the slotted tube and the "T" connection were located 10 inches from the base of the barrier unit. Each barrier unit was reinforced using three #5 longitudinal reinforcing bars, 11 feet, 8 inches in length. These bars were lapped with the three bars anchoring the "T" connection. The longitudinal reinforcing bars were skewed to lap with the dowel bars used to anchor the slotted tube connection.

The Office of Safety questioned the strength of the 12-inch long connection detail and requested that you conduct MASH Test 3-11, which you did. The vehicle was redirected and remained upright, and the occupant risk values were within the limits set by MASH. The test data summary sheet is attached for reference.

Findings
We concur in your request that the modified T-LOC concrete barrier segments that have been successfully crash tested to AASHTO MASH TL-3 conditions at a segment length of 12 feet will be considered acceptable for use on the NHS connection details when the segments are manufactured to a length of 12 feet. Please note the following standard provisions that apply to the FHWA letters of acceptance:

 

Sincerely yours,

Signature of David A. Nicol
David A. Nicol
Director, Office of Safety Design
Office of Safety

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