Not always. Got a classic one round here; the old railway bridge at Llanpumpsaint in Carmarthenshire has been marked at 12’3" for as long as I can remember. A year or so ago, the council put advance warning signs up on several approach roads which state that there is a 12’6" bridge a few miles ahead.
Now my wagon is 12’ 6" , measured it meself when I got it and as far as I’m concerned the marked height on the bridge is the maximum allowed. So I assumed they’d re-measured it after resurfacing, and instead of my usual five mile detour to get to one of my customers I went direct; only to find when I got to the bridge that nothing had changed and the ■■■■ thing was still officially three inches lower than me lorry. Needless to say I didn’t attempt it.
Luckily there’s enough room to turn round so it just cost me a bit of time; but one day somebody ain’t going to be so observant or have my local knowledge. Have to wonder if the council would end up with some sort of liability if the bridge DID get hit?