Moving alternate to underground trains

A proposal from the London architecture firm NBBJ suggests rethinking the city’s underground subway system entirely — replacing the trains with a system of moving sidewalks.

It’s so crazy it just might work. The NBBJ proposal — as of now in the very early concept phase — is entirely serious and includes some interesting notions and numbers.

The NBBJ plan would turn the 27.4 km Circle Line loop in the London Underground into a moving three-lane walkway. These are the moving sidewalks you see in airports, only with three adjacent walkways in a highway-type design in which lanes get faster as you move away from the platform.

The British, by the way, call these moving platforms “travelators,” which we can all agree is an altogether superior word for this sort of futuristic thinking. So let’s stick to that.

In passenger terminals, the initial step-on travelator lane would move at 4.8 kmph. The middle lane would ramp the speed up to 9.7 kmph and the outside fast line would clock in at around 14.45 kmph. Once travellers leave the station, however, the lanes would speed up, with a top speed of about 24.1 kmph on that outer express lane.

That might be perplexing, if you think it though, but variable-speed travelators are already a reality. The technology involves magnetic platforms and overlapping plates that allow a continuous walkway to slow down and speed up. In fact, just such a system in already in use at Toronto’s Pearson airport.

Here’s where the numbers get interesting: London’s Circle Line — the loop in question here — runs its trains at around 32.1 kmph between stations, but they’re notoriously crowded and prone to delays. A traveller on the express travelator, moving continuously at up to 24.1 kmph with no stops, would make the full circuit of the loop about five minutes faster than by train.

According to NBBJ, the travelator system could fit within existing London Underground tunnels — with existing trains and tracks removed, naturally. Entering, exiting and paying fares would remain largely unchanged. And since the entirety of the tunnel would be filled with moving people, rather than spaced-out passenger trains, the system could handle at least three times as many travellers at any given time.