1200 New Jersey Ave., SE

 Washington, D.C. 20590

March 29, 2011 

In Reply Refer To: 

HSST/B-218 

Mr. Paul Fossier, P.E.

Assistant Bridge Design Administrator

Louisiana Department of Transportation and Development 

Bridge and Structural Design Section, Rm. 608J 

Baton Rouge, LA 70804-9245 

Dear Mr. Fossier: 

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: F-Shape Reinforced Concrete Barrier with Slotted Drain Holes

Type of system: Permanent F-Shape Reinforced Concrete Barrier

Test Level: National Cooperative Highway Research Program (NCHRP) Report 350 

Test Level 4 (TL-4) 

Testing conducted by: Texas Transportation Institute (TTI)

Date of Request: December 9, 2010 

Drawing Designator: SBC04d 

You requested that we find this system acceptable for use on the NHS under the provisions of the 

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. 

FHWA memorandum “ACTION: Identifying Acceptable Highway Safety Features” of 

July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers. 

Decision

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

• F-Shape Reinforced Concrete Barrier with Slotted Drain Holes

Description

The Louisiana Department of Transportation and Development (La DOTD) currently uses

a cast-in-place concrete bridge rail on Louisiana bridges. The F-Shape bridge rail is 32 inches in 

height and 13.25 inches wide at the base. Presently, for bridges that use this concrete F-Shape

bridge rail, drainage is provided only at the ends of the bridge since there is no opening provided 

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through the bridge rail. La DOTD has proposed the use of 6 inches high x 24 inches long open 

slots located 10 feet apart at the base of the rail to accommodate drainage through the railing. 

Details of the proposed bridge rail are provided as enclosure to this correspondence. 

Crash Testing

The proposed La DOTD F-Shape Reinforced Concrete Barrier with Slotted Drain Holes (barrier) 

was analyzed at the test facilities at the TTI Proving Grounds Riverside Campus. The analysis 

was to evaluate the geometry and placement of the drainage slots on the barrier with respect to 

vehicle impact performance requirements for the NCHRP Report 350, TL-4 specifications.

The proposed drainage slot details were compared with other barriers systems utilizing similar 

type slots. This review consisted of comparisons with the Texas Department of Transportation 

(TXDOT) Single Slope Concrete Barrier (Wildlife Crossing) Precast SSCB (TXDOT Wildlife 

Crossing Barrier) and the Washington Pin & Loop Barrier System designed and successfully 

crash tested by TTI for the Washington State Department of Transportation (acceptance letter 

HSSD/B-206). The TTI researchers performed a similar review of the TXDOT Wildlife 

Crossing Barrier for TXDOT with respect to the size and potential interaction of these openings 

with respect to the small car and pickup truck for the NCHRP Report 350 crashworthiness 

criteria. 

The potential for vehicular interaction with the barrier was evaluated with respect to the criteria 

in the AASHTO LRFD Bridge Design Specifications (AASHTO). Two figures are presented in 

the AASHTO that provide general guidelines for the crash performance of barrier that contain 

openings or penetrations. These figures provide guidelines for the preferred post set-back from 

the face of the railing elements and the preferred ratio of the rail contact widths to the overall 

height of the bridge rail system (see AASHTO Figures A13.1.1-2-Potential for Wheel, Bumper, 

or Hood Impact with a Post; and, A13.1.1-3-Post Setback Criteria). The potential for wheel 

interaction with the opening in the barrier was investigated. For the proposed barrier design, the 

post setback from the face of the rail elements was considered to be zero (0) inches. The 

maximum vertical clear opening distance between the bridge top of the bridge deck and the top 

of the opening is 7-5/8 inches. Based on this information and the information provided in 

AASHTO Figure A13.1.1-2, the clear opening height of 7-5/8 inches presents a low potential for 

vehicular interaction with the opening in the barrier during a vehicular crash. 

The ratio in height of the contact length of the F-Shape Barrier to 32 inches total height of rail 

(i.e., rail contact width to height) is 0.762. Based on the proposed barrier geometry and the 

information provided in AASHTO Figure A13.1.1-3, the proposed barrier is considered 

marginal.

Findings

The analysis of the drainage slot used in the Washington State Department of Transportation 

Pin & Loop Barrier (WSDOT barrier) appeared to perform well in LS-DYNA impact 

simulations with both the small car and pickup truck. Although the WSDOT barrier did not meet 

the AASHTO Manual for Assessing Safety Hardware test specifications, the 9-inch high 

drainage slot specified used in the WSDOT barrier system did not adversely affect the 

performance of the crash vehicle. In addition, the potential for vehicle interaction with the 

drainage slot opening was considered low to marginal with respect to the criteria as provided in 

AASHTO Section 13 specifications. Based upon the researchers’ analysis, the F-Shape barrier 

with drainage slots is considered acceptable with respect to Report 350 TL-4 performance 

criteria.

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Details including a side-by-side comparison between size openings of TXDOT Wildlife Crossing 

Barrier, WSDOT barrier, and LaDOTD F-Shape Barrier with drainage slots are provided as 

enclosure to this correspondence. 

Therefore, the system as described in the request 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: 

• This acceptance is limited to the crashworthiness characteristics of the system and does 

 not cover their structural features, nor conformity with the Manual on Uniform Traffic 

 Control Devices. 

• Any changes that may adversely influence the crashworthiness of the system will require 

 a new acceptance letter.

• Should FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the system being marketed is 

significantly different from the version that was crash tested, we reserve the right to 

modify or revoke our acceptance. 

• You will be expected to supply potential users with sufficient information on design and 

 installation requirements to ensure proper performance. 

• You will be expected to certify to potential users that the hardware furnished has 

essentially the same chemistry, mechanical properties, and geometry as that submitted for 

acceptance, and that it will meet the crashworthiness requirements of the FHWA and the 

NCHRP Report 350. 

• To prevent misunderstanding by others, this letter of acceptance is designated as number 

 B-218 and shall not be reproduced except in full. This letter and the test documentation 

upon which it is based are public information. All such letters and documentation may be 

reviewed at our office upon request. 

• This acceptance letter shall not be construed as authorization or consent by the FHWA to 

use, manufacture, or sell any patented system for which the applicant is not the patent 

holder. The acceptance letter is limited to the crashworthiness characteristics of the 

candidate system, and the FHWA is neither prepared nor required to become involved in 

issues concerning patent law. Patent issues, if any, are to be resolved by the applicant.

Sincerely yours, 

Michael S. Griffith

Director, Office of Safety Technologies

Office of Safety 

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9-inch high drainage slot used in the WSDOT Pin & Loop Barrier system did not adversely 

affect the performance of the crash vehicle. In addition, the potential for vehicle interaction with 

the drainage slot opening was considered low to marginal with respect to the criteria as provided 

in AASHTO Section 13 specifications. Figure 7 shows the side-by-side comparisons between 

the size of the openings between the TXDOT Wildlife Crossing Barrier, Washington Pin & Loop 

Barrier, and the LaDOTD F-Shape Barrier with drainage slots. 

131

4"

6"

23

8"

32"

7

5

8"

31

4"

6"

12"

8"

42"

25

8"

TXDOT WILDLIFE CROSSING

SSCB BARRIER

LADOTD F-SHAPE BARRIER

431

2"

251

4"

47

8"

34"

9"

WADOT PIN &

 LOOP BARRIER

8"

Figure 76 – LaDOTD F-Shape Barrier, TXDOT Wildlife Crossing Barrier WSDOT Pin & Loop 

Barrier Cross-Sections 

TTI researchers have reviewed the current details of the LaDOTD Cast-in-Place Barrier 

Railing (F-Shape Barrier with Drainage Slots) details as shown in Figure 1. Based on TTI 

researchers’ review, the F-Shape barrier with drainage slots as shown on Figure 1 (LaDOTD 

Drawing Cast-in-Place Barrier & Transition (Transition on Wingwall)) is considered acceptable 

with respect to NCHRP Report 350 TL-4 performance criteria. 

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