This sign is attached to the railway bridge over the Leeds & Liverpool Canal near Gargrave.
You'll have seen similar ones elsewhere. They ask short-sighted drivers of high-sided vehicles to report any instances of their lorries or buses striking the bridge so that "The Rail Authority" (whoever that is) can check them for damage because, as they say, "The safety of trains may be affected."
But take a closer look at that wording:
I know the railways are extremely safety-conscious, but surely someone here is having a laugh?
And if you're wondering what sort of a flimsy, rickety old structure can both support the weight of passing trains but also be vulnerable to a glancing blow from a boat travelling at 3 mph then here it is: