AD Imagine, if you can, a world without cars, a world where road traffic moves at the speed of the pedestrian, the pedal cycle and the horse-drawn cart. It’s not a silent world: the noises are just different – the shouting of street vendors, the clatter of hooves and iron-shod tyres on cobbled roadways, the jingling of bicycle bells and the whistle of steam engines. But it’s an alien world, where the streets literally run with pollution from the millions of horses on which the economy depends, where long-distance travel is governed by the tyranny of the train timetable, where a town only 10 miles (16km) from the nearest railway station can seem as remote as though it were in the middle of nowhere. It’s a world that has changed only gradually over the past 100 years, with the coming of the railway, the biggest transport revolution since the Middle Ages. There are, indeed, road-going steam traction engines, but they’re big, unwieldy brutes weighing several tons whose iron w