Originally Posted by
unterhausen
Do they really allow trucks to go on roads where changing lanes means you hit an obstruction? I wouldn't have thought that to be the case.
It is. Many bridges and underpasses all over the US have arched clearances where there's more head room at the center than either or both sides. They'll be marked with multiple clearance signs over each lane, and if done properly the sign will give the lowest clearance for that lane (which is usually at the edge).
See article and photos here. BTW- The minimal clearance standard for the interstate system is 14' with most clearances more than that.
Normal motorists don't usually read clearance signs (which is why so many destroy bikes on roof racks) but a professional driver should be aware of their importance.
That said, there's a low clearance railroad overpass near me that's hit so often that lower edge of the Hi-flange is kept polished and rust free.