Fascinating article in the Guardian about the London Underground, including the to me rather mind-boggling thought that at any given moment during the rush hour, the tube has, at 600,000, the same population as Glasgow – the UK’s 4th largest city; along with this aside on the origins of the word ‘commuter’:

“Commute” in its original sense means to give something in exchange for something else, or to change one thing into another. A criminal sentence might be “commuted” from, say, hanging to life imprisonment. The word crossed over to use in a railway context in the US, where regular travellers began to swap day tickets for better-value season tickets; they “commuted” their daily tickets into season tickets.