They had little sections of pipes strung like so many wind chimes a hundred feet or so from an overpass near here. Truckers regularily hit them after reading clearance signs far back. Some still proceeded on after the racket they must have made and hit the overpass. Dislodging it once and shutting it down for inspection several times. They finally raised the Interstate overpass costing muco dinero.
There is a tunnel under a RxR from the Civil War days that has been hit many many times. They have several signs and it takes more than a little while for Truckers to back up when they go too far and turn down or up an old two lane rd.