U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Safety

eSubscribe
eSubscribe Envelope

FHWA Home / Safety / Roadway Departure / Safety Acceptance Letter

Safety Acceptance Letter B-215

Download Version
PDF [552 KB]

DOT logo
U.S. Department of Transportation
Federal Highway Administration

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

February 10, 2011

In Reply Refer To:
HSST/B-215

Ms. Karla A. Lechtenburg, MSME
Research Associate Engineer
Midwest Roadside Safety Facility
527 Nebraska Hall
Lincoln, NE 68588-0529

Dear Ms. Lechtenburg:

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

Name of system: Free Standing F-Shaped Temporary Concrete Barrier System
Type of system: Temporary Barrier
Test Level: American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3)
Testing conducted by: Midwest Roadside Safety Facility (MwRSF)
Date of request: August 17, 2010
Date initially acknowledged: August 29, 2010
Task Force 13 Designator: SWC09 (same as existing)

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

Requirements
Roadside safety devices should meet the guidelines contained in the MASH.

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

Description
The test installation was 62.34-m (204.5 feet) in length and consisted of sixteen (16) 3,810-mm (12 feet 6 inches) long, F-shaped temporary concrete barriers placed on the concrete tarmac without any attachment between the barriers and the tarmac. The concrete used for the barriers consisted of Iowa’s Barrier Mix, with a minimum 28-day concrete compressive strength of 34.5 MPa (5,000 psi). The minimum concrete cover varied at different positions of rebar in the barrier. Minimum concrete cover of 51 mm (2 inches) was used along the top of the vertical stirrup rebar and the bottom longitudinal rebar. Minimum concrete cover of 44 mm (1-3/4 inches) and 25 mm (1-inch) were used along the sides of the vertical stirrup rebar and at the rebar around the anchor bolt block, respectively. All steel reinforcement in the barrier was ASTM A615 Grade 60 rebar, except for the loop bars which were ASTM A706 Grade 60 rebar. Barrier reinforcement consisted of three (3) No. 5 and two (2) No. 4 longitudinal bars, twelve (12) No. 4 bars for the vertical stirrups, and six (6) No. 6 bars for the anchor bolt block reinforcement loops. Each of the five longitudinal rebar was 3.71 m (12 feet 2 inches) long. The vertical spacing of the lower, middle, and upper longitudinal bars were 165 mm (6-1/2 inches), 368 mm (14-1/2 inches), and 780 mm (29 1/8 inches) from the ground to their centers, respectively. The 1,829-mm (72 inches) long, vertical stirrups were bent into the shape of the barrier with varied spacing longitudinally. The 889-mm (35 inches) long anchor bolt block loops were bent into a U-shape and were used to reinforce the anchor bolt area. The barriers used a pin and loop type connection comprised of two sets of rebar loops on each barrier interconnection. Each loop assembly was configured with three (3) ASTM A706 Grade 60 No. 6 bars that were bent into a loop shape. The vertical pin used in the connection consisted of a 32-mm (1-1/4 inches) diameter x 711-mm (28 inches) long round bar composed of ASTM, A36 steel. The pin was held in place using one (1) 64-mm wide x 102-mm long x 13-mm thick (2-1/2 inches x 4 inches x 1/2 inches) ASTM A36 steel plate with a 35-mm (1 3/8 inches) diameter hole centered on it. The plate was welded 64 mm (2-1/2 inches) below the top of the pin. A gap of 92 mm (3 5/8 inches) between the ends of two (2) consecutive barriers was formed from the result of pulling the connection taut. Design details are provided as enclosure to this correspondence.

Crash Testing
Physical crash test for TL-3 as per MASH requires that longitudinal barrier systems be subjected to the following two full-scale vehicle crash tests:

  1. Test Designation 3-10. A 1,100-kg (2,425-lb) passenger car impacting at a nominal speed and angle of 100.0 km/h (62.1 mph) and 25 degrees, respectively.
  2. Test Designation 3-11. A 2,270-kg (5,004-lb) pickup truck impacting at a nominal speed and angle of 100.0 km/h (62.1 mph) and 25 degrees, respectively.

Only test designation 3-11 was conducted for the free-standing temporary barrier system described within the description section of this correspondence.

In addition, as per MwRSF email correspondence dated January 28, 2011 regarding test designation 3-10, no testing of the 1100C vehicle was conducted as part of the MASH testing of the F-shape PCB because the small car test is considered less critical due to lower impact energy and deflection. Also, previous testing of safety shapes with small cars has historically proven successful.

Findings
The analysis of the crash test results showed that the Free Standing F-Shaped Temporary Concrete Barrier System impacted with 2270P test vehicle as per MASH adequately contained and redirected the vehicle with controlled lateral displacements of the barrier system. There were neither detached elements nor fragments which neither showed potential for penetrating the occupant compartment nor presented undue hazard to other traffic. Deformations of, or intrusion into the occupant compartment that could have caused serious injury did not occur. The test vehicle did not penetrate nor ride over the temporary concrete barrier system and remained upright during and after the collision. Vehicle roll, pitch, and yaw angular displacements were noted, but they were deemed acceptable because they did not adversely influence occupant risk safety criteria nor cause rollover. After collision, the vehicle’s trajectory revealed minimum intrusion into adjacent traffic lanes. In addition, the vehicle exited the barrier within the exit box. Therefore, test designation 3-11 as conducted on the free-standing temporary concrete barrier system was determined to be acceptable according to the TL-3 safety performance criteria found in MASH. A physical crash test summary is included as enclosure to this correspondence. In addition, the requested waiver of test designation 3-10 and reasoning as provided within this correspondence is also accepted.

Therefore, the system described in the requests 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:

 

Sincerely yours,

/* Signature of Michael S. Griffith */

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

Enclosures

Page last modified on June 24, 2011.
Safe Roads for a Safer Future - Investment in roadway safety saves lives
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000