Mind your step

Following on from its supersonic Concorde aircraft and elaborate network of high speed trains, France has found yet another means of transport for speeding things up. Thanks to an accelerating moving walkway, commuters and tourists can now run as fast as an athlete through the underground corridor linking Paris’ Montparnasse metro stop and train station.
This conveyor belt, which was installed in 2002, accelerates pedestrians from a relatively low speed at the walkway’s entrance to a speed of 9 kilometers per hour in the middle section, before decelerating at the end of the walkway, all the while covering a distance of 180 meters from start to finish. To successfully execute these various changes in speed, the conveyor belt uses carpets made of tiny, independently rotating metal wheels.
Though exceedingly practical and trendsetting – Toronto Airport has also introduced an accelerating walkway – the conveyor belt at Montparnasse station is miniscule compared to the most ambitious and extensive walkway ever built.
That walkway – an elevated loop, covering more than three kilometers of the French capital during the Paris Exposition of 1900 – consisted of two electrically driven parallel platforms, one moving at 3.6 kilometers per hour and the adjacent one at twice that speed.
Why not once again install longer systems, allowing people to be conveyed around cities at high speeds and commuters to travel faster from A to B, without having to wait for a bus? This is, briefly stated, the research objective of Indraswari Kusumaningtyas, a PhD student at the Faculty of Mechanical, Maritime and Materials Engineering. In her doctoral thesis, entitled ‘Mind Your Step’, she explored the possibilities of utilizing much longer walkways.
Sadly, Kusumaningtyas reports that any long distance platforms built today should not be longer than 1.5 kilometers: “If commuters have to stand for more than ten minutes on a walkway, they’ll grow impatient. Since walkways are still quite slow compared to buses or trains, 1500 meters is about the maximum distance. Make them longer and they’ll cease to be competitive.”
Making the walkways faster is also not really an option. “12 kilometers per hour is about the maximum. If you go any faster than that, you get a strong sensation of wind, and it becomes scary. Some people, especially the elderly, simply cannot deal with that speed.”
Nevertheless, constructing a belt that covers a distance of 1.5 kilometers would be a huge step. Kusumaningtyas uses a computer model to study what constraints such long walkways would have to contend with.
She believes the biggest problem lies in the belt tension dynamics, which is influenced by the belt’s elasticity. Current systems use a single drive unit, but in longer belts, this results in higher dynamics.
“If, for security reasons, you must suddenly stop the motor that drives the belt, the belt section that is furthest away from the motor will still continue to move, owing to the elasticity. The belt, which comprises the walkway surface, will then become unstable. And you can’t solve this problem by making the belt stiffer. The belt has to remain flexible, because it must make a sharp bend at the end of the trajectory, where it disappears in a loop under the ground.”
The coal mining industry could be of help here, as some companies transport their bulk material via conveyor belts that are up to 20 kilometers long. Coal companies must also contend with annoying belt dynamics, and for this they use multiple drives to keep the tension steady along the entire length of the belt.
“We would probably have to do the same with long walkways – add many more drives,” Kusumaningtyas surmises.
Unfortunately for the walkway, the load it must convey changes all the time. People hop on in groups or individually, and they do so whenever it suits them. People may also stand or walk on the walkway. Consequently, each drive must respond individually to the weight it must convey at any given moment. This makes the system very complicated.
Or, as Kusumaningtyas puts it: “You can’t control the feed rate of people to a walkway like you can feed coal to a conveyor belt.”

Following on from its supersonic Concorde aircraft and elaborate network of high speed trains, France has found yet another means of transport for speeding things up. Thanks to an accelerating moving walkway, commuters and tourists can now run as fast as an athlete through the underground corridor linking Paris’ Montparnasse metro stop and train station.

This conveyor belt, which was installed in 2002, accelerates pedestrians from a relatively low speed at the walkway’s entrance to a speed of 9 kilometers per hour in the middle section, before decelerating at the end of the walkway, all the while covering a distance of 180 meters from start to finish. To successfully execute these various changes in speed, the conveyor belt uses carpets made of tiny, independently rotating metal wheels.

But only 180 meters? Why leave it at that? In her doctoral thesis, entitled ‘Mind Your Step’, PhD student at the Faculty of Mechanical, Maritime and Materials Engineering Indraswari Kusumaningtyas explored the possibilities of utilizing much longer walkways.

Though exceedingly practical and trendsetting – Toronto Airport has also introduced an accelerating walkway – the conveyor belt at Montparnasse station is miniscule compared to the most ambitious and extensive walkway ever built.

That walkway – an elevated loop, covering more than three kilometers of the French capital during the Paris Exposition of 1900 – consisted of two electrically driven parallel platforms, one moving at 3.6 kilometers per hour and the adjacent one at twice that speed.

 Why not once again install longer systems, allowing people to be conveyed around cities at high speeds and commuters to travel faster from A to B, without having to wait for a bus? This is, briefly stated, the research objective of Kusumaningtyas.

Sadly, Kusumaningtyas reports that any long distance platforms built today should not be longer than 1.5 kilometers: “If commuters have to stand for more than ten minutes on a walkway, they’ll grow impatient.”

Making the walkways faster is not really an option. “12 kilometers per hour is about the maximum. If you go any faster than that, you get a strong sensation of wind, and it becomes scary. Some people, especially the elderly, simply cannot deal with that speed.”

 Nevertheless, constructing a belt that covers a distance of 1.5 kilometers would be a huge step. Kusumaningtyas uses a computer model to study what constraints such long walkways would have to contend with.

She believes the biggest problem lies in the belt tension dynamics, which is influenced by the belt’s elasticity. “If, for security reasons, you must suddenly stop the motor that drives the belt, the belt section that is furthest away from the motor will still continue to move, owing to the elasticity. The belt, which comprises the walkway surface, will then become unstable and people will fall.”

“You can’t solve this problem by making the belt stiffer. The belt has to remain flexible, because it must make a sharp bend at the end of the trajectory, where it disappears in a loop under the ground.”

The coal mining industry could be of help here, as some companies transport their bulk material via conveyor belts that are up to 20 kilometers long. Coal companies must also contend with annoying belt dynamics, and for this they use multiple drives to keep the tension steady along the entire length of the belt.

 “We would probably have to do the same with long walkways – add many more drives,” Kusumaningtyas surmises.

 Unfortunately for the walkway, the load it must convey changes all the time. People hop on in groups or individually, and they do so whenever it suits them. People may also stand or walk on the walkway. Consequently, each drive must respond individually to the weight it must convey at any given moment. This makes the system very complicated.

 Or, as Kusumaningtyas puts it: “You can’t control the feed rate of people to a walkway like you can feed coal to a conveyor belt.”