July 11,2002

Refer to: HSA-10/CC78

Barry D. Stephens, P.E.
Senior Vice President, Engineering
03617 Cincinnati Avenue
Rocklin, CA 95765

Dear Mr. Stephens:

Your June 10 letter was delivered to Mr. Richard Powers of my staff on July 3 by Mr. Douglas Bernard.  In that letter, you requested the Federal Highway Administration's (FHWA) acceptance of a re-designed truck mounted attenuator (TMA) called the Safe-Stop 180 TMA for use on Federal-aid projects as an National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 3 (TL-3) device.  To support your request, you provided copies of a June 2002 report by E-TECH Testing Services, Inc., entitled "NCHRP Report 350 Crash Test Results for the Safe-Stop 180 TMA."  This report contained data on the NCHRP Report tests 3-50 and 3-51, which are the basic tests required for acceptance of a TMA. Optional TMA tests 3-52 and 3-53 were not run on this new version of the Safe-Stop.

The Safe-Stop 180 is 4190-mm long, 2360-mm wide at the impact face, and weighs approximately 945 kilograms.  Unlike the original Safe-Stop which had a tranport height of over 13 feet when in the raised position, the Safe-Stop 180 TMA consists of a bi-folding articulating frame assembly that contains a Safe-Stop Type A Cartridge immediately behind the impact face and a Safe-Stop Type B Cartridge near the support vehicle.  The Type A and B cartridges are similar in internal design to the Type 1 and Type 2 cartridges used with the original Safe-Stop, but are wider. When the rearmost frame containing the Type A cartridge is pivoted 180 degrees vertically and folded on top of the front frame containing the Type B cartridge for tranport, the unit is only 6'-8" high. A schematic drawing of the Safe-Stop 180 is included with this letter as Enclosure 1.

Enclosure 2 includes summary data on the two tests that were run.  In both tests, the support vehicle weight was 8550 kg.  This vehicle was blocked to prevent forward movement in the small car test, and rolled forward 6.9 m after impact by the pickup truck. The ridedown acceleration for the driver of the support vehicle in test 3-51 was not noted in the test report.

Based on the information you provided and staff analysis of the data, we agree that the Safe-Stop 180 TMA, as designed and tested, meets the appropriate crash evaluation criteria suggested in NCHRP Report 350 for a TL-3 truck-mounted attenuator. It may be used on the National Highway System (NHS) when such use is requested by a State transportation agency. As with all TMAs, this acceptance is based on its reported crash test performance and is not intended to address other factors such as durability, the mobility of the support vehicle, road-induced vibrations, maintainability, or the influence of moisture and temperature variations.  Since it is a proprietary product, its use on the NHS is subject to the provisions of Title 23, Code of Federal Regulations, Section 635.411 when such use is specified by the contracting agency.

Sincerely yours,

(original signed by Harry W. Taylor)


Carol H. Jacoby, P.E.
Director, Office of Safety Design

2 Enclosures

Sec. 635.411 Material or product selection.

(a) Federal funds shall not participate, directly or indirectly, in payment for any premium or royalty on any patented or proprietary material, specification, or process specifically set forth in the plans and specifications for a project, unless:

(1) Such patented or proprietary item is purchased or obtained through competitive bidding with equally suitable unpatented items; or

(2) The State highway agency certifies either that such patented or proprietary item is essential for synchronization with existing highway facilities, or that no equally suitable alternate exists; or

(3) Such patented or proprietary item is used for research or for a distinctive type of construction on relatively short sections of road for experimental purposes.

(b) When there is available for purchase more than one nonpatented, nonproprietary material, semifinished or finished article or product that will fulfill the requirements for an item of work of a project and these available materials or products are judged to be of satisfactory quality and equally acceptable on the basis of engineering analysis and the anticipated prices for the related item(s) of work are estimated to be approximately the same, the PS&E for the project shall either contain or include by reference the specifications for each such material or product that is considered acceptable for incorporation in the work. If the State highway agency wishes to substitute some other acceptable material or product for the material or product designated by the successful bidder or bid as the lowest alternate, and such substitution results in an increase in costs, there will not be Federal-aid participation in any increase in costs.

(c) A State highway agency may require a specific material or product when there are other acceptable materials and products, when such specific choice is approved by the Division Administrator as being in the public interest. When the Division Administrator's approval is not obtained, the item will be nonparticipating unless bidding procedures are used that establish the unit price of each acceptable alternative. In this case Federal-aid participation will be based on the lowest price so established.

(d) Appendix A sets forth the FHWA requirements regarding (1) the specification of alternative types of culvert pipes, and (2) the number and types of such alternatives which must be set forth in the specifications for various types of drainage installations.

(e) Reference in specifications and on plans to single trade name materials will not be approved on Federal-aid contracts.