September 5, 2003
Barry D. Stephens, P.E.
Senior Vice President - Engineering
Energy Absorption Systems, Inc.
3617 Cincinnati Avenue
Rocklin, CA 95765
Dear Mr. Stephens:
Your May 22, 2003, letter to Mr. Richard Powers of my staff consolidated previously-submitted information with additional test data on an impact attenuator named the FastBrake and requested formal FHWA acceptance for its use on the National Highway System (NHS). Included with that letter were copies of a May 2003 test report prepared by E-TECH Testing Services, Inc., entitled "NCHRP Report 350 Crash Test Results for the FastBrake System". On August 5, 2003, your representative, Mr. Douglas Bernard, delivered some final information that had been requested by my staff to aid in our review.
The FastBrake attenuator is a modified version of your current BrakeMaster which was accepted as a Report 350 terminal/attenuator via FHWA acceptance letter CC-41, dated June 19, 1997. While the BrakeMaster required a separate transition design when used to shield a concrete barrier, the FastBrake has a backup assembly that includes tubular steel stiffeners, a rear cable anchor, a standoff bracket, and a wheel deflector. It is intended to shield temporary concrete barrier and must be attached to an unanchored concrete safety shape a minimum of 6.1-m long as tested. This 6.1-m segment may be a single precast section or two 3.0-m (or 3.8-m) segments spliced together as shown in Enclosure 1B. Barrier segments beyond the initial 6.1-m segment may be shorter, but all require use of a Report 350 pin and loop (or equal) connection. Since the front four bays and the attenuator nose are identical to the original BrakeMaster, any of the front anchor options approved for use with the BrakeMaster may also be used with the FastBrake attenuator, design details for which are shown in Enclosures 1A and 1B.
You ran three tests on the FastBrake: NCHRP Report 350 tests 3-31, 3-37, and 3-38, the summary results of which are shown on Enclosure 2. In test 3-37, the initial impact point was 0.3 m downstream from the nose of the FastBrake and the pickup truck was contained and redirected. In test 3-38, the centerline of the truck was aimed at the center of the concrete barrier and the test vehicle was again redirected. Based on the successful outcome of all three new tests, the FastBrake is classified as a non-gating redirective crash cushion at test level 3 and it may be used on the NHS at the discretion of the contracting authority.
You also requested that the FastBrake be accepted for use in bi-directional locations with the fender panels lapped in opposite directions on each side, noting that a head-on crash into a bi-directional configuration would prove satisfactory because the first bay does not collapse and would prevent vehicular contact with the reverse-lap panels. For a head-on impact, this seems to be a reasonable assumption, but for a left-of-center, end-on hit, the impacting vehicle would likely yaw clockwise, making the passenger compartment vulnerable to contact with the open ends of the reverse-lap panels. However, considering the low probability of such an impact when the FastBrake is used to terminate a median barrier, I am willing to waive test 3-30 on the bi-directional unit on the condition that median or other bi-directional installations be monitored by your company to verify acceptable field performance and that the results of this in-service evaluation be reported to my staff within two years from the date of this letter.
Please note the following standard provisions that apply to FHWA letters of acceptance:
(original signed by John R. Baxter)
John R. Baxter, P.E.
Director, Office of Safety Design
Office of Safety