The two plates are joined using carefully-torqued boltsīreakaway points are generally located close to ground level. When the upper post is impacted, the plates slip and bolts sever (or pop out).An upper post (with a plate at its base) is situated above.A lower post (with a plate on its top) is put into the ground.A basic slip system is assembled as follows: This joint allows the pair to break apart at an intended juncture. Instead of a single post rise continuously up out of the ground, a slip base approach joins two separate posts via connector plates. Multidirectional slip base from Roadside Design Guide, 2011, by the American Association of State Highway and Transportation Officials, Washington, D.C. One of the clever technologies employed to help posts break properly is known as a slip base system. Slip bases and other breakaway designs are all around us, supporting signs and other infrastructure.

Whether made of wood or metal, such supports have to be well-engineered to withstand winds, storms, tsunamis and earthquakes.Įvery so often, though, these posts are called upon to do something crucial but fundamentally opposed to their primary function: when hit by a vehicle, they need to break in just the right way in order to help reduce vehicular damage and save lives. Most of the time, the posts holding up highway signs and street lights have one job: to stand up straight and provide support.

Breakaway bolts