U.S. Department 

Of Transportation 

Federal Highway 

Administration

400 Seventh St., S.W. 

Washington, D.C. 20590 

February 27, 1996 

Refer to: HNG-14/SS-61 

Mr. Leon J. Witman, Jr. 

Regional Federal Highway Administrator 

Portland, Oregon 

This is in response to your January 3 office memorandum requesting the Federal 

Highway Administration’s, (FHWA) Office of Engineering acceptance of the subject 

breakaway sign support. You referenced the report of bogie vehicle testing, titled 

“Testing of a Modified Oregon Mulit-Directional Slip-Base Sign Support, FOIL Test 

Numbers: 95F007 and 95F009,” and dated June 1995, which we obtained on February 5. 

Our requirements for breakaway supports are those in the American Association of State 

Highway and Transportation Officials (AASHTO), Standard Specifications for Structural

Supports for Highway Signs, Luminaires and Traffic Signals. We also recognize the 

testing and acceptance guidelines found in the National Cooperative Highway Research 

Report number 350 Recommended Procedures for the Safety Performance Evaluation of

Highway Features. 

The sign supports consisted of a 200-mm by 200-mm steel tube post with a wall 

thickness of 4.3 mm welded to a triangular slip-bas. The base had three 90-degree 

notches to accept the three 1-inch (25.4-mm) diameter bolts. Bolted to the top of the post 

was an “H” shaped bracket to which an extruded aluminum sign panel was attached. The 

three bolts clamped the sign post to a matching foundation stub and were torqued to the 

manufacturers recommended torque of 102 N.m. The rectangular washers used were 25 

mm thick, 50 mm wide and 200 mm long. The bolt threads in each test were lubricated 

before sign installation. A 0.53-mm (25 gage) slip-bolt keeper place was used to 

maintain the 343-mm bolt circle diameter. The sign stub was bolted to the FOIL 

runway’s foundation plate. An 839-kg bogie vehicle fitted with a 10-stage crushable 

nose, was used to simulate an impacting automobile. A summary of the testing follows: 

Test Parameter / Test # 95F007 95F009 

Mass of test article 386 kg 386 kg 

Impact speed 35.9 km/h 101.4 km/h 

Velocity change 7.0 m/s* 2.7 m/s 

Occupant impact speed 2.2 m/s 2.7 m/s 

Stub Height 95 mm 95 mm 
* The base of the sign caught on the framework of the bogie vehicle and slowed the 

vehicle during a much longer time interval than is normal. This result is unlikely in an 

impact with an automobile. 

These results meet the change-in-velocity and stub height requirements adopted by the 

FHWA and ASSHTO. Therefore, the modified Oregon multi-directional slip-base sign 

support described above and illustrated in the enclosures is acceptable for use on the 

National Highway System within the range of conditions tested, if requested by a State. 

The following conditions and limitations also apply unless further crash testing indicates 

acceptability under other conditions: 

1. No more than one sign support may be used within a 2.1-meter width. 

2. All supports shall be mounted to a structural concrete foundation that will 

not move in the soil if the support is struck by a vehicle. 

3. Mass of sign, post, and other hardware above the couplings shall not 

exceed 450kg. 

Our acceptance is limited to the breakaway characteristics of the slip-bas and does not 

cover the structural features of the support. Presumably, the State will develop sufficient 

information on structural design and installation requirements to ensure proper 

performance. 

 Jerry L. Poston 

Geometric and Roadside Design Acceptance letter No. SS-61