Sure, it’s one heck of a pipe dream — or a Tube dream, in this instance. But isn’t the notion of walking (with mechanical assistance) along a subway line instead of cramming into a rolling aluminum box with hundreds of your fellow commuters rather enticing, especially if you can get from point A to B in the same amount of time or less and enjoy a light cardio workout in the process?

That’s very much the idea — swapping out traditional subway rolling stock for a high-speed moving walkway — behind a new proposal from NBBJ, the global architecture firm behind the biodome-studded Amazon campus that will soon dominate downtown Seattle, the gargantuan glass donut that serves as Samsung’s new Silicon Valley headquarters and other high-profile commissions.

The concept was presented as part of a New London Architecture-hosted design competition seeking "hypothetical but realistic proposals to make London a better place."

The subway line in question is the London Underground’s almost-not-underground, not-quite-a-circle-anymore Circle line, which spirals in a lasso shape through the heart of London along a 17-mile, 36-station course. Like the District, Hammersmith & City and Metropolitan lines, the perpetually packed Circle line is notable for not being a true “tube” line — that is, its not part of the network of deep-level tracks buried far beneath the streets of London. Instead, the shallow-tunneled line is sub-surface in nature with a small handful of stations being completely above ground.

The moving walkway at the heart of NBBJ’s vision of a train-free Circle line isn’t too different from standard moving walkways — or travelators, if you’re a Brit — common in airports (Dallas Love Field had the first and Charles de Gaulle Airport in Paris has the most futuristic-chic), Disney theme parks and sprawling Las Vegas casinos where they're employed to suck tourists right off the Strip. Moving walkways are also a fixture in large public transit networks, the London Underground included, where they connect adjacent but too-far-to-hoof it stations and platforms.

And much like many other early mind-blowing innovations, moving sidewalks made their grand debut at the world's fair — 1893’s World Columbian Exposition in Chicago, to be exact. Another early mechanical moving sidewalk appeared at the 1900 Exposition Universalle in Paris. A New Jersey-based inventor/vintner/dreamer named Alfred Speer even hoped to bring moving sidewalks to the crowded, turn-of-the-century streets of New York City as a permanent fixture.

That obviously never happened.

A rendering of a proposed moving walkway that would replace trains on London's Circle Line. Rendering: NBBJ

What sets between NBBJ’s conceptual design apart from conventional pedestrian conveyor belts is that the Circle line’s moving walkway would be a three-lane/three-speed affair, with each lane allowing commuters to zip along at different speeds. The yellow walkway, functioning as a sort of entrance/exit lane, starts off at a minimum speed of 3 mph (roughly the standard for airport-style moving walkways) before gaining a maximum speed of 9 mph between stations. In the middle, the orange walkway reaches a maximum speed of 12 mph. And finally, for those really in a rush, the red walkway, which appears to be lined with benches, reaches a maximum speed of 15 mph.

Of course, whichever of the three subterranean moving sidewalks a pedestrian ultimately decides to traverse/stand on depends on the distance they need to travel and, most likely, their comfort level. Those going just a couple of stops from, let’s say, Westminster to Blackfriars, would likely want to stay put in the yellow lane. Those with longer commutes might want to opt to travel along the zippier orange or red walkways.

Whatever the case, NBBJ’s concept does indeed enable London commuters to potentially move faster by travelator than by train. Plagued by delays and congestion, Circle line trains top out at a max speed of 20 miles per hour between stations. A commuter traveling along red walkway, the “fast lane,” at the average walking speed of 3 mph could easily get to their destination before a perpetually stopping-and-going train traveling along the same route.

“The result would be considerably quicker, more enjoyable and healthier journeys,” claims NBBJ, which, in addition to the Circle line’s subway-replacing-walkway, has also conceived a “shadowless skyscraper” design for London.

The Circle line, one of the oldest and most hated upon lines in the London Underground system, carries an estimated 114 million commuters annually.

A rendering of a proposed moving walkway that would replace trains on London's Circle Line. Rendering: NBBJ

One standard moving walkway feature noticeable absent from NBBJ’s conceptual renderings would appear to be handrails. While the presence of a 3 mph yellow “feeder lane” helps to ease on/off spills, it’s easy to imagine that things could get messy — and dangerous — very quickly if commuters, with nowhere to clutch on to, start to loose their balance and topple over en masse, particularly when exiting.

Ladies and gentlemen, please be advised that there is a human pileup at Shepherd’s Bush Market.

In 2002, Paris experimented with a high-speed moving walkway, trottoir roulant rapide, at Montparnasse-Bienvenüe Station, a chaotic Metro hub linking four major subway lines. With the goal to dramatically cut the amount of time that it took commuters to travel between lines along a slow, traditional moving walkway, a high-speed walkway reaching a speed of 7.5 mph was installed. Even with handrails, commuters were falling over left and right. And so, the walkway’s speed was slowed to 6 mph. Still, commuters continued to take spills on and while attempting to exit the walkway, which was also beset with frequent technical issues. After a few short years, the walkway was reverted back to its sluggish, original speed.

As for NBBJ’s concept for the London Underground, it will likely forever remain just that — a concept. Still, it’s a nice bit of city-improving, stress-reducing fantasy making … so long as you’re able to keep your balance.

Via [Dezeen], [Wired]

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.