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A Carbon-Free, Stackable Rental Car

An MIT group hopes that its foldable electric vehicles will cut pollution, and ease congestion.

The Smart Cities group at the MIT Media Lab is working on two low-cost electric vehicles that it hopes will revolutionize mass transit and help alleviate pollution. Next week, the group will unveil a prototype of its foldable electric scooter at the EICMA Motorcycle Show, in Milan. A prototype for the team’s foldable electric car, called the City Car, is slated to follow next year.

City car: The Smart Cities group at MIT’s Media Lab is developing a shared-use electric car (top) that folds and stacks like a shopping cart. A working prototype of the car will be unveiled next year. (Note: The top image is an illustration.) The bottom image shows a close-up of a half-scale wheel prototype with built-in suspension and electric motors.

The MIT group sees the vehicles as the linchpin in a strategy that aims to mitigate pollution with electric power, expand limited public space by folding and stacking vehicles like shopping carts, and alleviate congestion by letting people rent and return the vehicles to racks located near transportation hubs, such as train stations, airports, and bus depots.

“We’re looking at urban personal mobility in a much more sustainable way than the private automobile provides,” says William Mitchell, director of the Smart Cities research group.

The group’s strategy will efficiently solve the “last mile” problem without losing the virtues of the private automobile, Mitchell says. The last mile is that inconvenient distance between any major transit stop and a person’s final destination. While a traditional automobile provides mobility on demand and gets you to your destination, its negative externalities–congestion and pollution–seem intractable.


  • Watch a rendering of how City Cars will fold and stack.

At the heart of these vehicles is an omnidirectional robot wheel that the team has developed. The wheel encases an electric-drive motor, as well as suspension, steering, and braking systems. With no engine or mechanical parts between the wheels and the driver’s controls, the system offers great flexibility in design. The driver can, in fact, fold the car up (see below image). Six to eight folded and stacked City Cars can fit into one conventional parking space. General Motors sponsored the development of the car.

This illustration shows how City Cars stack together.
Credit: Franco Vairani

The wheels also enable incredible maneuverability. Instead of making U-turns, the car can spin on the spot, and when the driver turns each wheel 90 degrees, the car can parallel-park by moving sideways.

“The idea for a wheel motor has been around for a long time,” says Peter Schmitt, designer of the wheel. But Schmitt says that the advantage of his design is that the wheel is controlled by software instead of by mechanical coupling.

The MIT team’s vision of deploying these cars in a shared-use, personal-mobility system isn’t new either. In Lyon, France, a company called Velo’v recently introduced a shared-use bicycle system throughout the city. Based on its initial success, the Velo’v system is being extended to Paris with approximately 2,000 stacks and 20,000 bicycles.

Another business model that the team has looked at is the Zip Car rental system.

Zip Car is a rental service based on a two-way model: customers have to return the car to the same location from which they picked it up. They also have to reserve cars online in advance.

The MIT team says that the Zip Car two-way model is great for neighborhoods where people have to boomerang in and out to run errands. But in a dense city starved for parking, the MIT designers see great virtue in their one-way system, which lets people move from spot to spot without returning to their point of origin. In the ideal City Car scheme, vehicles can be rented from one rack and returned to another.

Still, Robin Chase, the founder and former CEO of Zip Car, has some reservations about the MIT group’s system. She says that she’s worried about logistical and operational problems, such as the even distribution of vehicles. With a one-way model, too many could wind up in one location. The company must then pay for trucks to redistribute the cars or scooters throughout the city.

Chase adds that when she was with Zip Car, she noticed that customers were reluctant to adopt new technologies. “Our electric car was our least rented vehicle,” she says. “People didn’t seem to trust the technology.”

The MIT team is not deterred. It’s looking at Taipei as an ideal location in which to roll out the electric scooter, which was developed in partnership with SYM, a major Taiwanese scooter manufacturer. “Taipei is teeming with scooters,” says Ryan Chin, a designer with the Smart Cities group.

Currently, there are nearly as many scooters in Taiwan as there are people. During a typical rush hour, traffic lanes overflow, and riders wear surgical masks to filter the pollution from exhaust. Some three million scooters lie abandoned throughout the country.

“If a shared scooter is used by 10 different people a day, you’ll reduce the number of scooters on the road by half,” Chin says.

With a successful run at the Milan motorcycle show, Chin says that his group’s 50-kilogram scooter could be mass-produced and deployed within three years.

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