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 1930’s that contains thousands of interlocking levers and switches.

Human dispatchers use light boards as well as pencils and paper to track the movements of trains from a total of 22 subterranean “towers” that operate on a 24 hour basis.

These human operators monitor the progress of individual trains while also responding to phone calls and keeping their ears open for two-way radio transmissions.

ny subway controls

The teams responsible for the repair and maintenance of these systems are now compelled to manufacture their own replacement components, since the original parts have long since fallen out of production.

New York City is finally undertaking measures to upgrade these key parts of its subway infrastructure that date from around the time of the Great Depression.

The Metropolitan Transportation Authority (MTA) plans to replace the old signalling equipment with digital technology that will computerise the operation of the subway system and dramatically increase efficiency levels.

They expect the upgrades to enable nearly twice as many trains to travel safely along a given subway route in close proximity.

The process has already commenced in earnest, with the L line between Manhattan and Brooklyn now using a new digitised, automated signalling system, and the upgrade of the No. 7 line to Queens slated for completion by 2017.

The L line’s new system enables around two dozen trains to move in both directions per hour along a route that takes 37 minutes to circumnavigate on average. This is a dramatic increase in potential passenger volume, given that the preceding system could only accommodate 15 trains per hour.

Give the sheer size of New York’s underground rail network, which consists of nearly two dozen major lines and over 1200 kilometres of track, a full and comprehensive upgrade of its signalling system is expected to take multiple decades to complete.

This means that those antiquated parts of the subway system which should really be museum fodder could remain in operation for at least another two decades.

The MTA remains confident however, that the original equipment will hold up until its digital successors are installed.

“This stuff is old but it works –  it works really well,” said MTA spokesman Adam Lisberg.