This is NOT a sign I came across in person. I saw it on Sjaak Lucassen's site from his around-the-world tour. Great sign!
At the entrance to the Wrynose and Hardknott passes in the Lake District. In the summer you can smell clutch and brake fibre burning on both these passes as most UK car drivers are not used to 1 in 3 hills with hairpin bends (or the concept that something might come in the opposite direction on the single width road resulting in needing to reverse on the same hills. )
