First post so not sure if I'm doing this right
But during the construction lately in Texas I've noticed TXDOT moving away from hanging signs on overpasses and rather installing typical metal over head signs instead. Is there a reason for this that anyone knows of?
Large signs mounted on bridges do introduce an additional wind load on the bridge, creating another stressor. Thought to be saferto mount a sign on a gantry designed to specifically handle the sign(s).
Yes, many jurisdictions are phasing them out. Not just because of the wind stressing issue Big John mentions, but MnDOT has found that they also weaken the bridges and introduce additional locations for water intrusion (no matter how well sealed).
And those signs can occasionally fall off a bridge as well.
(Ohio moved to stop attaching signs to bridges after one fell off along the eastern portion of the Columbus outerbelt (aka I-270) some years (I think 10) back.
I'd imagine the signs get in the way of maintenance, like painting, as well.
Not to mention that they are also prone to falling off during earthquakes, despite Caltrans continuing to put them up because nostalgia reigns supreme in the Golden State.