Lorry drivers unfortunately often get sent daily on completely new routes, covering hundreds of miles per day. Road closures, traffic congestion and a hundred other things can mean that they have to take a different route to the one anticipated, even on a route they've done before. If satnavs were truly fit for purpose, they'd have an option to take into account size of vehicle (in all directions) and bridges/narrow country lanes/etc, but most of them don't. Driving an HGV means taking into account not hitting the kerb as you turn, not taking out the turns too much while still making it round, observing everything round you at all times while also reading hundreds of signs every mile, observing traffic ahead and figuring out where you're going. When roads then also don't have the appropriate signage at the start (like a narrow country lane near us...starts off looking like a lovely lane wide enough for two cars, goes round a bend and suddenly becomes narrow enough that taking some cars down it is a challenge even if you don't meet anything else-no warning of this at the entry to the road), it becomes just about impossible.
I don't drive HGVs, but an ex of mine did. She hasn't hit any bridges, but she's come close (as in turned down the road to discover she couldn't go further) twice-once as she was focussing on the traffic and didn't see the warning sign til she was a bit close, the other because there wasn't a warning sign...apparently someone had nicked it.
Just occasionally, someone makes a mistake. It's commonly known as being human and no matter how conscientious, it's going to happen.
