As recounted before, my favourite 'road closed' sign ever was one in France: "Route barrée - même aux cyclistes". They know what cheeky sods we normally are.
I think I prefer the ones used by the Hinckley Connection project, which had a cyclist, walker and equestrian exception stuck to them. A pity more roadworks do not use them, because it is most commonly the case that roadworks can be walked past, even if work is in progress.