The tech behind smart cities

Forget flying cars, city dwellers have more to gain from cars that stack.

The idea of folding cars isn't new, but as urban parking spots become increasingly rare (and expensive), it's begun to look more promising.

As a Ph.D. student at MIT, Mitchell Joachim was part of a group of researchers who came up with the idea of stackable cars. More than 10 years later, he's still hoping that car manufacturers will start producing cars like them. (He's developed a new iteration of the folding cars at his firm, Terreform ONE, a Brooklyn-based lab that experiments with innovative green designs.)

Ideally, the cars would be owned by the city and used by residents for daily commuting, alleviating traffic congestion. (There's been interest from governments in Spain and Berlin, but the funding has fallen short so far.)

Think of it as a bike-sharing system merged with Zipcar.

"When you're done using it, you'd leave it for other people," said Joachim.