One of the world's most iconic cities is in the process of upgrading a subway network whose key infrastructure systems date from before the Second World War.

While New York City is host to the largest mass transit network in the United States,  carrying as many as 6 million passengers per day, critical parts of its operating technology date to well before the Second World War. The signalling system in particular is strikingly antiquated, consisting of electro-mechanical equipment built in the…