Now here's a nugget of information for parties. Sorting through photos of Paris, I realise that French trains run on the left. Wikipedia reveals that trains often do not operate on the same side of the road as cars do. In France, for instance, the first train lines were built by British engineers, so kept to the left. The Paris RER trains keep left, but have to operate on separate tracks within the Paris Metro area which was designed to run on the right. Another anomaly occurs in the Alsace-Moselle region, where trains keep to the right because the lines were built in the late 19th century when Alsace-Moselle had been part of Germany. Bridges at the former border allow the trains to swap sides.