Breakaway Posts

by:

Michael S. Stenko
President, Transpo Industries

Breakaway or frangible posts should be used on all posts located close to the road. The use of these breakaway or frangible devices will make the posts less rigid thereby safer when impacted by an errant motorist.

Full scale crash testing, required by the new proposed NCHRP 350 update in the United States, has shown that some multiple post sign panel designs currently in use are not capable of resisting the forces exerted when one of the support posts is impacted. The result is the inability of the impacted post fuse/hinge plates to activate, which could cause the failure of all of the remaining frangible bases. It is critical for safety that a multiple post sign should remain standing and be supported by the posts not impacted. The post fuse/hinge plates are critical components in the resultant change in velocity of the vehicle and passengers.

Research is needed to study the structural characteristics of ground mounted sign panels that are currently installed on multiple posts, This research should include a survey of sign panel designs currently in use and subsequent modeling of each design. Simulation crash testing should be performed with both the small car and pickup truck. Simulation should be verified by full scale crash testing. The final report would result in minimum sign panel design criterion for use on multiple post ground mounted signs with either breakaway posts or base assemblies with fuse/hinge plates.

How do we get this research funded and started?

Mike Stenko has over 25 years in the industry and has been with Transpo for over 16 years. He is a member of TRB, ACI, ASCE, Chairman of ACI Comm. on Polymers Concrete. Sub-Comm. Chair of AASHTO/AGC/ARTBA Taskforce 13 Subcommittee on highway signs and luminaries.