December 1, 1997

 Refer to: HNG-14

Mr. J. M. Essex

Vice President, Sales

Energy Absorption Systems, Inc.

One East Wacker Drive

Chicago, Illinois 60601

Dear Mr. Essex:

 

On November 21, you and members of your company met with Messrs. James Hatton and

Richard Powers of my staff. You delivered a letter addressed to me dated November 19 which

requested the FHWA to accept the QuadGuard - Low Maintenance Cartridge (LMC) System as a

National Cooperative Highway Research Program (NCHRP) Report 350 test level 3 (TL-3) crash

cushion. You also provided us copies of a report entitled “QuadGuard - LMC System

Qualification to NCHRP 350 Engineering Summary” dated November 1997, which included the

E-Tech report, “NCHRP Report 350 Crash Test Results for the QuadGuard-LMC System”, and a

videotape of the tests that were conducted. The QuadGuard-LMC is a reusable, partially selfrestoring crash cushion that utilizes the main components of the Report 350-qualified QuadGuard

except for the energy dissipation cartridges, which have been replaced with elastomeric cylinders

of the type used in your Report 230-qualified Low Maintenance Attenuator (LMA).

The QuadGuard-LMC unit tested was an 11 bay unit 10 163 mm long and 1220 mm wide. It

consisted of a monorail assembly anchored to a concrete pad, steel diaphragms, steel fender

panels, a nose assembly, and a steel strut backup. The rear-most nine bays contained energyabsorbing elastomeric cylinders as shown in the cutaway view in Enclosure 1. This drawing also

identifies the system elements that are identical to those used in the previously-accepted

QuadGuard unit.

Enclosure 2 is a summary of the tests that were run and the results of each. We noted that some

changes were made in the design as testing progressed and agree that these changes were of such

a nature that all tests in the series you presented are valid for qualifying the QuadGuard-LMC at

TL-3.

We noted also that the QuadGuard - LMC was tested at temperature extremes expected to be

seen in service and performed well in both cases. Although my October 29 letter to you suggested

that Test 3-30 might be more critical at the reduced attenuator temperature of -31.8 degrees C (-

25.2 degrees F), you responded that Test 3-32 would result in higher occupant impact velocities
2

as a result of friction between the monorail and the laterally-loaded front diaphragms. We

compared the data from Tests 3-30 and 3-32 that were used to qualify the standard QuadGuard as

a Report 350 crash cushion and confirmed that the occupant impact velocity was slightly higher in

the angle hit on the nose (Test 3-32) than on the head-on hit (Test 3-30).

My October 29 letter also requested information on and an analysis of your proposed transition

designs from the QuadGuard LMC to a typical concrete safety barrier. You indicated in your

report that the tension strut backup was demonstrated to be a rigid structural member by Test 3-

38 in the original QuadGuard certification series and that there was no measurable deflection at

this point. Figure 9 of your report (Enclosure 3) shows your recommended offset layout when

your QuadGuard series attenuators are used to shield the ends of concrete barrier in a bidirectional traffic situation. When used in a gore area, we assume the attenuator will be centered

on the barrier, the tension strut backup will be used, and the width of the unit will exceed the

bottom width of the concrete to minimize the snagging potential. We further assume that when

the QuadGuard LMC is used to terminate a metal-beam barrier system at bi-directional sites, the

transition designs already tested for the original QuadGuard will be specified and used.

Based on our review of the individual test reports and the crash test videos that were provided to

us, we agree that the QuadGuard-LMC, as tested, meets the acceptance criteria for an NCHRP

Report 350 Test Level 3 (TL-3) crash cushion. Therefore, it may be used on the National

Highway System (NHS) when such use is requested by a transportation agency. Since the

QuadGuard is a proprietary device, its use on Federal-aid projects, except exempt, non-NHS

projects, is subject to the conditions stated in Title 23, Code of Federal Regulations, Section

635.411, a copy of which is Enclosure 4.

Sincerely yours,

(original signed by Dwight A. Horne)

Dwight A. Horne

Chief, Federal-Aid and Design Division

4 Enclosures

Acceptance Letter CC-43