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                Safety Eligibility Letter B-127
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-127
                          **Date:**
            06/18/2004
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            NYSDOT
                          **Device Description:**
            TL-4 box-beam transition designs
                          **View PDF:**
            b127.pdf (99.54 KB)
    
    Skip to contentSkip to contentUnited States Department of Transportation - Federal Highway AdministrationJune 18, 2004
Refer to: HSA-10/B-127

George A. Christian, P.E.Deputy Chief Engineer (Structures)State of New York Department of TransportationAlbany, New York  12232

Dear Mr. Christian:

In your May 22 letter, you requested the Federal Highway Administration's acceptance of a box-beam guiderail to bridge rail transition design as a test level 4 (TL-4) design for use with several standard bridge railing designs currently used in New York.  The design was successfully crash tested to TL-3 at the Texas Transportation Institute (TTI) and documented in that agency's April 2004 report entitled "NCHRP Report 350 Test 3-21on the New York State DOT (NYSDOT) Modified Box Beam Transition to 4-Rail Steel Bridge Rail." This design is shown in the enclosure to this letter.

Based on the successful test of the transition to a 4-rail, deck-mounted bridge railing, you also requested acceptance of this transition design when connected to a two-rail bridge rail with a brush curb, a three-rail design flush-mounted, a four rail design mounted behind a sidewalk, and a five rail combination rail design.  Each of these applications may be considered acceptable with the following caveats:

With the two-rail curb-mounted bridge rail, the lower rubrail is not used, so the curb must be flared away from the roadway and extended under the transition to reduce the likelihood of a vehicle's wheel snagging on the leading edge of the curb.
With the three-rail bridge rail, the design remains as tested, but the fourth rail is eliminated.
With the five-rail design, the added upper rail may be terminated in a manner similar to the fourth rail in the tested design or flared behind the fourth rail.Although not physically tested when connected to a concrete safety shape bridge railing, TTI completed a finite element analysis of this configuration and predicted that this transition when used in conjunction with a curb that blocks out the lower leading edge of the concrete safety shape would likely meet NCHRP Report 350 evaluation criteria at TL-3.  Based on this analysis, I will consider the NYSDOT designs BD-RC 3, BD-RC13-R1, and BD-RC16-R1 at http://www.dot.state.ny.us/caddinfo/structures/bd.html to be acceptable also.

As noted in your letter, the single-unit truck test used to verify TL-4 performance is less demanding than the pickup truck test because the impact speed and angle are less and the large tires of the single-unit truck are much less likely to snag on any transition elements.  Transition designs equal in height to your tested design have been successfully crash tested with the single-unit truck.  Therefore, each of the transitions listed above may be considered TL-4 designs as requested.  However, as with all roadside safety designs, field performance should be monitored to verify their assumed crashworthiness.


Sincerely yours,
(Original Signed By R. Powers)for:John R. Baxter, P.E.Director, Office of Safety Design 
Office of Safety
Enclosure U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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