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Design and Testing of a Dual Support Breakaway Sign




Gene Paulsen, Brian Pfeifer, James Holloway, John Reid




The Missouri Highway Transportation Department (MHTD) has been using a dual leg breakaway roadside sign supports with a perforated tension fuse plate. A very important feature of this system is the ability of its support to release upon impact and swing up and out of the way when impacted by an errant vehicle. Another critical feature of the sign system is its ability to withstand wind loads without causing structural damage to the system. A modified dual support breakaway sign system is proposed which improves both of these criteria. Recently, MHTD added a multi-directional slip base to the breakaway sign design details. MHTD wished to evaluate the performance of the multi-directional slip base and the dual support breakaway system when impacted by a vehicle at some angle other than perpendicular to the face of the sign, to correspond to actual roadside data. Two full-scale vehicle crash tests were conducted on the dual support breakaway sign and multi-directional slip base. The safety performance of the system was determined to be acceptable according to criteria set forth by Naitonal Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. Changing the material of the fuse plate ASTM A36 steel to A572 Grade 50 steel created a stronger connection that significantly improved the wind load capacity of the sign system without hindering its safety performance.


Highway Signs, Breakaway Supports, Slip Base, Wind Loads, Highway Safety, Crash Tests

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