The ACCEL Moving Sidewalk From ThyssenKrupp Is a Dream Come True

CC BY 2.0. Lloyd Alter

While in Spain to look at the very interesting MULTI elevator system, covered on TreeHugger here, I also rode the new ACCEL high speed moving sidewalk. For me personally, this really was a dream come true, and before I describe the ACCEL permit me to explain why. I was a bit of a boy inventor and when I was around sixteen I read a science fiction novel that described high speed moving sidewalks as the future city's major form of urban transportation. I wondered how they could work, how do you get from the slow speed you need to get on from a standing start to the high speed you want to get somewhere fast?

moving sidewalk

Lloyd Alter/ my sidewalk/CC BY 2.0

I spent a lot of time thinking and sketching and eventually had an idea based on Bernoulli’s principle, which is what causes water to move faster when you push it through a smaller hose. Because the fundamental problem with high speed moving sidewalks is that when they get faster, they need more stuff, whatever it is made of, passing any given point in a given time. My indulgent dad introduced me to a patent attorney and we did all the drawings, but my design had serious technical problems. (including: how do you solve the handrail?)

paralellogram sidewalk

Lloyd Alter/ sidewalk made of sliding parallelograms/CC BY 2.0

Then my patent attorney, looking up prior art, showed me another application that had such a superior method of getting more metal through a narrower space using parallelogram shaped platforms and hockey stick shaped entries, doing the same thing without the problems that I had; I knew I was beat and I shelved the whole patent application and started thinking about going into architecture school.

This was over forty years ago, and I was certain that we would be flying through our cities on hockey-stick shaped moving sidewalks by now, yet I never saw or heard about one ever being built. Because of course, we had roads and cars and who need invest in moving sidewalks? (Commenters are complaining "why not just walk?" but remember, these are high speed, going at 12 km/hr, well over twice the speed of walking. They are an alternative for transit, not walking.)

And in fact I never did see a multiple speed moving sidewalk anywhere until Toronto’s new Pearson Airport opened, which had the first ThyssenKrupp Turbo Track moving sidewalk. I was enchanted, running back through the corridor to ride it three times and to try and figure out how it worked. It was noisy and it was wobbly and it was out of order the next two times I was at the airport. But when it worked, it was amazing, and they even somehow solved the handrail. After those years of thinking about this, I was finally riding on it.

This is all my longwinded explanation of why I have become such a cheerleader for ThyssenKrupp, who have been kind enough to encourage me with access to press conferences and trips to see the model in Spain. It is also why I spent so much time in their research facility playing on their new ACCEL moving sidewalk, an upgraded version of the Turbo Track.

ACCEL from Lloyd Alter on Vimeo.

The ACCEL looks pretty much like Toronto’s Turbo Track, but is much quieter (it’s still noisy) and it is smooooooth. You get on it, standing on one of the smaller yellow-bordered rectangles, and soon find that they start separating and a bigger squarer pallet slides in between them. Very quickly you have a lot more metal moving much faster. At the other end, the big pallet starts sliding in under the one in front of it, the smaller ones touch again and you step off the slower speed belt.

at a glance

© ThyssenKrupp

Each pallet or square is connected to a linear induction motor, and each is precisely controlled; the big pallet follows a track that dips down while the small pallet keeps going. I tried really hard to screw it up, putting one foot in front of another (your feet separate when it starts going faster), standing on the big pallet instead of the small (you intuitively sort of adjust onto the smaller pallets as it slows).


Lloyd Alter/CC BY 2.0

I was worried that this is not something that people are used to, about safety; are there a lot of injuries, people not figuring it out? I was told that the accident rate is actually a bit less than with normal belt type moving sidewalks; most accidents happen at the end when people are not paying attention and spill off the moving belt, whereas with the ACCEL you get a lot of warning from the slowing sidewalk and know the end is near.

Accel returning from Lloyd Alter on Vimeo.

At the end, the pallets fly around really fast and run in the other direction; this is great for two way operations such as in a transit situation, they are already there so you don’t need a second installation.

endless screw

Lloyd Alter/ Endless screw/CC BY 2.0

Then there is the really vexing handrail problem. How do you get it to travel at two speeds? When I was working on the idea I just gave up and proposed a sort of roller skate on a track that would keep you from falling sideways, but just slid along with you. With the ACCEL there is this big honking variable pitch screw underneath that is somehow connected to a clutch in the handrail carts, so that it moves between the two speeds. I believe that the screw transitions and then runs the handrail cart for the last bit while the sidewalk is running slowly, while the handrail itself runs at the fast speed. Like I said, this is hard, but they have figured it out. It works.

Accel city

© ThyssenKrupp

The implications of this machine are significant for urban planners. It is well known that subway systems work better with fewer stops further apart (and subway stops are very expensive), while cities work better when they are closer together. (Toronto readers: This is why the proposed Scarborough subway is so insane) If systems like the ACCEL were installed between subway stops, they could provide more points of access, support more people and spread out the real estate development instead of piling it on top of the transit nodes. It’s a continuous, high volume way of moving people efficiently.

But for me personally, it is a lot more than that. Others keep asking “where are our flying cars?” But I have been asking for most of my life: “where are our high speed moving sidewalks?”

They’re here.