There are some brilliant minds working for the RTA.
The most interesting example of their brilliance is a particular stretch of road near where I live, that I daily travel on to get to work. The stretch I am referring to is the lead up to Tom Ugly's Bridge on the Sutherland side.
At the moment they are doing work on the truss bridge because its old and needs maintenance. So while they are doing this, they've diverted one of the 3 lanes over the other bridge and are now running the 2 remaining lanes down the center, so as to provide room for the work that needs to be done.
Now a truss bridge, by design, has beams that go over head, and thus provide a limit in vehicle height. This particular bridge also has overhead beams that make the outside lanes lower than the inside lane.
However since they've change the lane configuration the total upper height limit for the bridge has been reduced. Which they make blatantly clear by telling you with clear signage that the limit for that bridge is 4.5 meters and if you are over 4.5 meters you should take the lane that is now diverted over the other bridge which doesn't have that limit.
So if you're driving a truck that is, say, 5 meters tall you might be thinking when you see the sign (which is before that 90 degree corner), that you're sweet, all I have to do is move across to the inside lane and go across the other bridge. But as you come round that last big corner you'll probably either be hit with the sudden realisation that the pedestrian bridge that goes over the road is too low to accommodate your truck, or you will be hit by the pedestrian bridge that goes over the road and is too low to accommodate your truck.
Why is it that there are signs that clearly give the impression that vehicles over 4.5 meters can travel that route (albeit via the diverted lane), but fail to mention that any vehicle over 4.7 meters can not? Why can't people erecting these things give thought to the big picture and make signs that give drivers a clearer overview.
Perhaps they are. Perhaps there is a sign I'm not seeing. Perhaps its the truss bridge's old height.