Date of this Version
Transportation Research Report TRP-03-018-89
A modified turned-down guardrail terminal which uses retrofit clips to hold up the guardrail has been in use on Nebraska Highways for several years. During this time, the Nebraska Department of Roads has become aware of a problem with this design. After being exposed to temperature fluctuations and vibrations from passing traffic the retrofit clips expand and the guardrail drops to the ground.
Twelve different designs were tested on an actual guardrail field installation and a design consisting of strategically placed shear bolts was recommended.