July 11, 2003

Refer to: HSA-10/CC-83

Barry D. Stephens, P.E.
Senior Vice President of Engineering
3617 Cincinnati Avenue
Rocklin, California 95765

Dear Mr. Stephens:

In your June 13, 2003, letter, you requested the Federal Highway Administration's (FHWA) acceptance of a low-speed truck mounted attenuator (TMA) called the LS-Pro TMA for use on Federal-aid projects as a National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 1 (TL-1) device. As noted in your letter, tests for TMAs at impact speeds lower than 70 km/h (TL-2) are not formally recognized in Report 350. However, the crash test evaluation criteria for a low speed TMA would logically remain the same as those for higher speed impacts so a TMA that meets all performance requirements for a TL-2 device at the TL-1 impact speed of 50 km/h could be considered acceptable.

To support your request, you provided copies of a December 1994 abbreviated report by E-TECH Testing Services, Inc., entitled "Low Speed TMA Crash Test Report" and a June 2003 report entitled "NCHRP Report 350 Crash Test Results for the LS-Pro TMA." These reports contained data on modified versions of NCHRP Report 350 tests 2-50 and 2-51, which are the basic tests required for acceptance of a TMA. The only modification was the impact speeds, which were 50 km/h rather than 70 km/h.

The LS-Pro TMA consists of an aluminum cartridge with a Durashell nose, a backup assembly, and a backup support structure for attaching the unit to its support vehicle. Its total weight is approximately 409 kg. The LS-Pro components were initially used in your ALPHA 2001 MD TMA that was originally tested and accepted under NCHRP Report 230 guidelines in 1994. A schematic drawing of the LS-Pro TMA is included with this letter as Enclosure 1. Enclosure 2 includes summary data on the two tests that were run. The 8550-kg support vehicle was blocked to prevent forward movement in the small car test, and an 8595-kg support truck rolled forward 1.1 m after impact by the pickup truck.

Based on the information you provided and staff analysis of the data, I agree that the LS-Pro TMA, as designed and tested, meets the appropriate crash evaluation criteria inferred in NCHRP

Report 350 for a TL-1 truck-mounted attenuator. It may be used on the National Highway System (NHS) when impact speeds are expected to be in the 50-km/h range and its use is acceptable to the appropriate highway 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 Michael S. Griffith)

Michael S. Griffith
Acting Director, Office of Safety Design
Office of Safety

2 Enclosures