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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-235

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U.S. Department of Transportation
Federal Highway Administration

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

July 9, 2012

In Reply Refer To:
HSST/B-235

Mr. Vue Her
Transportation Engineer
Office of Roadside Safety and Cooperative Research
Division of Research and Innovation
California Department of Transportation
5900 Folsom Blvd., MS-5
Sacramento, California  95819

Dear Mr. Her:

This letter is in response to your request for the Federal Highway Administration (FHWA) to review a roadside safety system for eligibility for reimbursement under the Federal-aid highway program.

 

Name of system:

California Department of Transportation (CalTrans)
Low-Profile Reinforced Concrete Barrier

Type of system: Permanent Longitudinal Barrier
Test Level:

NCHRP 350 Test Level 2 (TL-2)

Testing conducted by: CalTrans Roadside Safety Research Group
Task Force 13 Designator: SGR45
Date of request: November 16, 2010
Date initially acknowledged: November 16, 2010
Date of completed package: May 1, 2012

Decision:
The following device is eligible, with details provided as attached as an integral part of this letter:

Based on a review of crash test results submitted by the manufacturer certifying the device described herein meets the crashworthiness criteria of the National Cooperative Highway Research Program (NCHRP) Report 350, the device is eligible for reimbursement under the Federal-aid highway program.  Eligibility for reimbursement under the Federal-aid highway program does not establish approval or endorsement by the FHWA for any particular purpose or use.

The FHWA, the Department of Transportation, and the United States Government do not endorse products or services and the issuance of a reimbursement eligibility letter is not an endorsement of any product or service.

Requirements
To be found eligible for Federal-aid funding, roadside safety devices should meet the crash test and evaluation criteria contained in the National Cooperative Highway Research Program (NCHRP) Report 350 or the American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware (MASH).

Description
The low-profile barrier test article was constructed at the Caltrans Dynamic Test Facility. The test article was 30.48 m (100 feet) long with a nominal height of 0.4572 m (18 inches).  It
consisted of a 0.305 m (12 inch) deep foundation, a 0.105 m (6 inch) curb, with nine 0.305 m (12 inch) posts spaced at 3.048 m (10 feet) on center, and a 3x8x3/8 inch structural steel rail. Because existing soils were non-homogeneous due to an assortment of previous projects at the construction location, a 2.44 x 0.61 x 30.48 meter (8 x 2 x 100 feet) soil bed was excavated then backfilled with soil from a local gravel provider.  The soil analysis of the fill soil was completed by the Caltrans Geotechnical Lab and classified as fine sandy silt.  At a 90% relative compaction and an optimum moisture content of 12.3%, the maximum dry density was 114.6 pcf.  Upon completion of the excavation, the bed was filled with soil, 0.1016 meters to 0.1524 meters (4inches to 6inches) per lift.  Each lift was moisture-conditioned and compacted using a vibratory roller.  After the bed was completely filled and compacted, a nuclear gauge was used to test the compaction.  The minimum relative compaction required was 90% under Caltrans 2006 Standard Specifications.  A 93% relative compaction was achieved with a density of 122.4 pcf.  The low-profile barrier was constructed and installed in two phases: pouring of the footing and attachment of the rail.  The soil was re-excavated 1.016 meters x 0.3048 meter x 30.48 meters (3.3 feet x 1 foot x 100 feet) to install the footing of the barrier.  The footing and the curb were constructed in one pour.

The footing was 30.48 m (100 feet) long and had 9 posts spaced 3.048 m (10 feet) on center. The rail came in 4 pieces and spanned 30.48 m (100 feet).

Once the formwork for the footing was complete, the reinforcing steel and anchor bolts were positioned and tied in.  Concrete was then poured into the formwork while being consolidated with a concrete vibrator.  All exposed steel components were galvanized from the manufacturer prior to installation. The footing was placed on December 4, 2009.  The posts and rails were installed on December 15, 2009. Because of the timing of the pour and when staff was available to test the compressive strength of the concrete, the 28-day test could not be conducted.  Instead, the compressive strength was tested at 31 days and was determined to be 40.6 MPa (5890 psi).

The adjacent pavement elevation varied along the length of the low-profile barrier.  Thus the height of the barrier ranged from 0.4572 to 0.4826 meters (18 inches to 19 inches).

Design details are provided as enclosure to this correspondence.

Summary and Standard Provisions
The low-profile barrier was crashed test in accordance with NCHRP Report 350 evaluation criteria.

Test 701 was tested at NCHRP Test Level 2 (Test 2-11). The vehicle tracked smoothly into the barrier, impacting 400 millimeters (15.75 inches) downstream of the 5th barrier post. The front tire (red) made contact with the sleeve of the rail 530 millimeters (20.8 inches) downstream of the center of the post.  The rear tire (green) made contact 1430 millimeters (56.3 inches) downstream of the post. The vehicle lost contact with the barrier at 0.412 seconds after impact. The impact speed and angle were 70.2 km/h and 25.3°, respectively.  The exit speed and angle were 62.3 km/h and 7.8°, respectively.  The vehicle remained upright during and after the impact and vehicle stability was considered satisfactory. Occupant risk factors satisfied the test criteria and the vehicle exit trajectory remained within acceptable limits.

Findings
Test 702 was performed at NCHRP Report 350 Test Level 2 (2-10). The vehicle tracked smoothly into the barrier. The front tire (red) made contact 1260 millimeters (49.6 inches) upstream of the 3rd barrier post.  The rear tire (green) made contact 630 millimeters (24.8 inches) downstream of the post.  The vehicle lost contact with the barrier at 0.364 seconds after impact.  The impact speed and angle were 70.8 km/h and 21°, respectively. The exit speed and angle were 63.1 km/h and 9.6°.  The vehicle remained upright during and after the impact and vehicle stability was considered satisfactory.  Occupant risk factors satisfied the test criteria and the vehicle exit trajectory remained within acceptable limits.
                                                           
Therefore, the system described and detailed in the attached form is eligible for reimbursement and may be installed under the range of conditions tested.

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

 

Sincerely yours,

/* Signature of Michael S. Griffith */

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

Enclosures

Page last modified on January 17, 2013.
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