Futuristic depictions of the 21st century in classic films often showed sprawling metropolises with flying cars, expansive urban development and any of a number of fanciful mass transit systems. The reality of the situation is that our transport systems have evolved to be bigger, faster and stronger versions of the systems of decades past. Even the most advanced supercar today still sits on four wheels, holds a couple of passengers and requires a driver, just as cars did almost a century ago.

But now, a novel solution is being proposed that could revolutionize urban transport, and with the rewards of decreased congestion, improved efficiency and greater environmental friendliness in sight, the world of autonomous personal rapid transport could be around the corner. On the other hand, there are some hurdles yet to be cleared.

The podcar system, as it's known informally, draws its foundations from the advantages of car use, but eliminates the disadvantages of owning and operating a car. The system uses a network of overhead rails snaking through the city atop existing streets and sidewalks with personal podcars whizzing around on them, taking users wherever they desire.

Each individual podcar would sit at predetermined stations littered throughout the city, available on-demand much like a taxi service. But while a taxi can be expensive because it requires capital, fuel and labor, the podcar system would be driverless - instead being guided by a computer and taking passengers to the desired podcar stop. Automation of the system means that costs are drastically reduced, making the system affordable for anyone that could afford other forms of mass urban transport. The system differs from current urban mass transport thanks to its on-demand nature, as well as the relative ubiquity of pod car stations - instead of scattered train stops the podcar would have almost the same accessibility that car usage provides.

According to the L.A. Times, building the podcar system could be up to 12 times cheaper than railway systems and the need for gasoline could be reduced dramatically if the system is run on electricity. At about $25 to $40 million per mile for the first systems, they won't be cheap, but compared to the $100 to $300 million price tags associated with rail and subway systems, it's a bargain.

While the idea may sound like something of a pipe dream, its being taken very seriously by urban planners in major cities. Korean company Vectus is testing a podcar system in Sweden, with ambitions of selling the system to the Swedish government, and the rest of the world eventually. A similar system, called ULTra (pictured), is already being built at Heathrow Airport in London as well.