t3

U.S.Department

of Transportation

Federal Highway

Administration March 30, 2000

400 Seventh St., S.W.

Washington. D.C. 20590

Refer to: HSA-CC64

Albert W. Unrath, Sr., P.E.

ALBERT W. UNRATH, INC.

P.O. Box 631

Colmar, PA 189150631

Dear Mr. Unrath:

In your February 28 letter, you requested the Federal Highway Administration’s (FHWA)

acceptance of your U-MAD 1OOK truck mounted attenuator (TMA) at the National Cooperative

Highway Research Program (NCHRP) Report 350 test level 3 (TL-3). To support your request,

you included copies of three test reports prepared by the Transportation Research Center in East

Liberty, Ohio, and videotapes of the tests that were conducted. After reviewing the material,

Mr. Richard Powers of my staffrequested additional drawings of your TMA. These were

delivered to him on March 21.

The U-MAD 1OOK TMA consists of an aluminum box containing eight separate internal

compartments filled with variable density energy-dissipating material. The unit is 3277~mm

(129 inches) long, 2286mm(90 inches) wide and weighs approximately 413 kg (910 pounds),

excluding the weight of the mounting bracket and lift mechanism which is 157 kg (346

pounds). A schematic drawing of the U-MAD 1OOK is shown as Enclosure 1.

Three NCHRP Report 350 tests were conducted: Test 2-50, Test 3-51, and Test 3-50. Test 2-50

is a 70 km/h head-on impact with the 820 kg car. The TMA support vehicle is blocked to

prevent any forward movement in this test. Occupant impact velocity was reported as 11.1 m/s

and the subsequent lo-ms ride down acceleration was 9.2 G’s Test 3-51, a 2000 kg pickup

track impacting head-on at 100 km/h, was conducted on January 12,200O. Occupant impact

velocity was reported as 12.0 m/s and the lo-ms ridedown acceleration was 19.1 G’s. The

support vehicle rolled ahead 6.17 m (20.25 feet) in this test. The final test (3-50), which was

the 820-kg car impacting an un-blocked support vehicle head-on at 100 kmh was conducted

on January 28,200O. Occupant impact velocity was reported to be 12.3 m/s and the lo-ms

ridedown acceleration was 15.7 G’s. Roll ahead distance for the support vehicle was 4.06 m

(13.33 feet).

Since the impact speed in test 3-50 was slightly higher than the nominal 100 km/h, we are

willing to accept the occupant impact velocity of 12.3 m/s which is 0.1 m/s higher than we have

previously considered to be the limit for acceptance. However, for both this test and test 3-51,

the evaluation criteria for occupant impact velocity and ridedown accelerations are at the upper

limits recommended by NCHRP Report 350. If impact speeds had been any higher or if the
support vehicle had a test inertial mass heavier than 8613 kg, the U-MAD 1OOK would not

likely have been acceptable at TL-3. Thus, it may be considered acceptable for use on the

National Highway System (NHS) at TL-3 provided its support vehicle is no heavier than the

S613-kg truck used for the test. If you wish to mount it on a heavier support vehicle, it must be

tested with that vehicle. If mounted on a lighter vehicle, the expected roll ahead distances will

be longer and the level of risk to the driver of the support vehicle will be increased. Therefore,

it should not be used on a shadow truck significantly lighter than 8613 kg without additional

testing.

This acceptance is based on the reported crash performance of the U-MAD 100K and is not

intended to address the long-term durability of the unit. Further, I am assuming that production

models will be identical to the nrototwe test units. Since the lJ-MAD l00K is a nrnnrietarv
129” (a27.-fcm) _ I .eq~“m?cm.

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Sec. 635.411 Material or product selection.

(a) Federal funds hall not participate, directly or indirectly, in payment for any premium or royalty

on any patented or proprietary matenal, 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

equallysuitable unpatented items; or

(2) The State highway agency certifies either that such patented or proprietary item is essential for

synchromzatron 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 tinished 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

thespecifications for various types of drainage installations.

(e) Reference in specifications and on plans to single trade name materials will not be approved on

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