Mark.....This is the sign of the times (pun) but it is not the first sign to warn of unsuitable roads for Lorries etc who rely on using Sat Nav.
In Colchester's Dutch Quarter there has been numerous HGVs stuck in the narror roads where old property overhangs the street. Not suitable for HGVs did'nt do much good. Now they have promenent "Don't Follow Sat Nav" signs as well. They have been there for a couple of months at least.