U.S. Department 

Of Transportation 

Federal Highway 

Administration

400 Seventh St., S.W. 

Washington, D.C. 20590 

January 4, 1991 

Refer to: HNG-14/SS-22 

Christopher Meyer, P.E. 

Product Development Engineer 

Trus Joist Corporation 

P.O. Box 7923 

2600 E. Amity Road 

Boise, Idaho 83707 

Dear Mr. Meyer: 

Thank you for your letter of December 13 to Mr. Thomas O. Willett in which you 

requested Federal Highway Administration (FHWA) acceptance for your company’s 

revised Type “L” MICRO=LAM laminated veneer lumber signposts as breakaway 

structures. Our letter of August 19, 1986, accepted the original MICRO=LAM design 

based upon full-scale crash testing in weak soil. In support of your current request you 

submitted reports dated November 1990,of tests conducted at the Southwest Research 

Institute. Four tests were conducted to assess the compliance of the MICRO=LAM post 

with a revised sawcut pattern with the breakaway requirements of the 1985 AASHTO 

Standard Specifications for Structural Supports for Highway Signs, Luminaires and 

Traffic Signals. These specifications have been adopted, with minor modifications, by 

the FHWA. The pendulum testing also included posts with the old sawcut design to 

permit comparison between the full scale and the pendulum test results. 

Testing was conducted using an 1,800-pound instrumented pendulum with a 10-stage 

crushable nose. The speed of the pendulum at impact was 20 mph (29.3 fps). Details of 

the tested 14 7/8 inch x 7 7/8 inch posts are shown in the enclosures. Test results are 

summarized below: 

Test Number TJ-10 TJ-11 TJ-12 TJ-13 

Sawcut Type Old New Old New 

Soil Type Strong Strong Weak Weak 

Pendulum Velocity Change 7.6 fps 9.0 fps *6.9 fps 8.2 fps

Est. 60 mph Velocity Change 7.2 fps 7.6 fps *6.9 fps 7.4 fps

Stub Height 3.0 in 3.0 in 3.0 in 3.0 in 

Weight of Test Article 319 lb 319 lb 319 lb 319 lb 
*Compare to 1986 tests with 1840# Rabbit: 

20 mph test, weak soil, velocity change 8.4 fps 

60 mph test, weak soil, velocity change 9.2 fps 

The above information shows that the tested posts meet the change in velocity and stubheight requirements adopted by the FHWA. Therefore MICRO=LAM posts spaced 

further than 7 feet apart with the new sawcut design are acceptable for use on Federal-aid 

projects when requested by a State. 

This acceptance is limited to breakaway characteristics of the posts and does not cover 

the structural features. Presumably, you will supply potential users with sufficient 

information on structural design and installation requirements to ensure proper 

performance. We anticipate that the States will require certification from Tros Joist 

Corporation that the posts furnished have essentially the same mechanical properties and 

geometry as those used in the tests, and that it will meet the FHWA change in velocity 

requirements. 

Since your company’s MICRO=LAM posts are proprietary items, to be used in a 

Federal-aid highway project they: (a) they must be supplied through competitive bidding 

with equally suitable unpatented items; (b) the State highway agency certifies that they 

are essential for synchronization with existing highway facilities or that no equally 

suitable alternate exists; or (c) they are used for research or for a distinctive type of 

construction on relatively short sections of road for experimental purposes. Our 

regulations concerning proprietary products are contained in Title 23, Code of Federal 

Regulations, Section 635.411, a copy of which is enclosed. 

 Sincerely yours, 

 L.A. Staron, Chief 

 Federal-Aid and Design Division 

Enclosures 

Roadside and Geometric Design Acceptance Letter SS-22