U.S. Department 

Of Transportation 

Federal Highway 

Administration

400 Seventh St., S.W. 

Washington, D.C. 20590 

August 31, 1989 

Refer to: HNG-14/SS-13 

Mr. Mark S. Granger 

Sign Post Sales Manager 

Marion Steel Company 

912 Cheney Avenue 

Marion, Ohio 43302 

Dear Mr. Granger: 

This is in response to your letter of August 8 to Mr. James Hatton requesting Federal 

Highway Administration (FHWA) acceptance of your company’s Rib-Bak sign posts in 

sizes from 2 to 4 pound-per-foot when used with a lap splice connection. You referenced 

a study done by the Texas Transportation Institute for the State of Arizona (Arizona 

Research Study HPR-PL-1-31 (202), “Small Sign Support Analysis”). The report 

contained dimensions and installation details, which are repeated here in the enclosure. 

The full-scale crash-testing phase of the study included four tests of triple post supports 

using 1,800 pound cars. The results of those four tests are as follows: 

Test No. Size of Posts 

in 

Installation 

Impact 

Speed 

Vehicle Change 

in Velocity 

Occupant 

Impact Speed 

Occupant 

Ridedown 

Accel. 

7024-24 4 lbs/ft 20.6 mph 28.0 fps 21.9 fps 2.7 g 

7024-25 4 lbs/ft 62.6 mph 13.2 fps 13.2 fps 0.6 g 

7024-26 3 lbs/ft 21.7 mph 12.6 fps 12.5 fps 0.5 g 

7024-27 3 lbs/ft 61.6 mph 9.1 fps No contact No contact 

Test 7024-24 did not meet the FHWA requirements for breakaway supports. An analysis 

of the energy expended during that test, however, allows us to accept the use of two 4 

pound-per-foot posts within a 7-foot span. Tests of the 3 pound-per-foot posts did meet 

breakaway requirements for change in velocity; therefore triple post installations of sizes 

from 2 to 3 pounds-per-foot are acceptable. 

It is noted that the sign supports were only tested in the “strong” soil described in the 

NCHRP 230. If you desire to offer this hardware to States for use in soil equivalent to 
the “weak” soil described in the NCHRP 230, we recommend additional tests be 

conducted in that soil type. 

In Summary, your company’s Rib-Back posts in “strong” soil using a stub/sign post 

where the stub is 4 inches high or less are acceptable for use on Federal-aid highway 

projects, if requested by a State, in the configurations shown in the matrix below. 

Installations using one or two posts, or those using lighter weight posts than those tested 

will result in less severe accelerations and velocity changes. Therefore, we are extending 

out acceptance to cover installations down to a single 2 pound-per-foot post. 

Post Size Acceptable Single Applications Dual Triple

2 lbs. Yes Yes Yes 

2 1⁄2 lbs. Yes Yes Yes 

2 3⁄4 lbs. Yes Yes Yes 

3 lbs. Yes Yes Yes 

4 lbs. Yes Yes No 

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

is 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 Marion Steel 

company that the hardware furnished has essentially the same chemistry, mechanical 

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

in velocity requirements. 

 Sincerely yours, 

 L. A. Staron, Chief 

 Federal-Aid and Design Division 

Enclosure 

Federal Highway Administration 

HNG-14:Nartimovich:gm:8-23-89:61331 

Copies to: 

HED-1 HNG-1 HNG-10 HNG-14 Reader, 3212 

Reader, 3128 Reader, 3206 File, 3128 

M. Hargrave, HSR-20 H. Taylor, HHS-12 

RAs w/enclosure