"Texas Goalpost" Assemblies -- Why do they fail so often?

[thenetwork]

First, for those of you who aren't sure about what "Texas Goalposts" are.  they are roadside assemblies that are single posts secured to the ground, but near the top it splits into a U-Shape, allowing for two separate signs to share the same post, side-by-side. 

I believe Texas was the first state to widely use them (hence the term Texas Goalpost).  Other states have used them, including Colorado and, more recently, Ohio, and are used mostly to display route duplexes, speed limits, etc,...

I like how it eliminates a second post needed to be secured to the ground, but one thing that I cannot stand about the Texas-styled assemblies and that is how easily they break, which results in the signs turning and facing in a different direction than originally intended.  This can happen from high winds or (like in Ohio) when snow from snowplows hit the signs in the right spot.  Then the sign is slightly, if not not visible to the drivers the signs are intended for, and it seems to take much longer for the DOTs to straighten out the signs than for them to replace a traditional sign that gets hit &/or knocked down.  I have seen signs askew for months in Colorado and Ohio before they are corrected/replaced.

If this type of assembly is used by quite a few states, why do they still break so easily?

[peterj920]

Have not seen that assembly in the Midwest.  Wisconsin mainly uses wooden posts, Minnesota uses narrow steel posts but puts an angled steel post as a brace in the back of their signs, I haven't seen that in any other state.

[roadman65]

FDOT does not use them regularly, but on FL 518 in Melbourne they are going EB with a US 1 shield east of I-95.  Generally we use one mono tube pole bolted to the ground (in older assemblies its planted) with two or three signs attached at the top mostly side by side, but its not split into a U.

[txstateends]

The turning and twisting has been surprising to me, with all the testing that has been done in the past on signs, guard rails, and other assorted installations over the years.  There is more than enough errant drivers, as well as wind, in TX that it should be second nature to make sure post assemblies aren't loose, or wouldn't come loose enough, to miss while driving past them on the road.

[Brian556]

This post system is prone to the post turning in the base casting. TxDOT is on it's third design of the casting, and it seems to be working better.

also, the goalposts would often snap off at the weld that connects the goalpost to the sleeve portion that slides over the vertical post. This would typically happen in strong winds to assemblies with extenders, which allow more than the standard amount of signs on them.

[briantroutman]

By "Texas goalpost" , you're referring to something like this? https://goo.gl/maps/fg47B

[thenetwork]

By "Texas goalpost" , you're referring to something like this? https://goo.gl/maps/fg47B

Correct.