http://cities.media.mit.edu/projects/citycar.html
The City Car is a stackable electric two-passenger city vehicle. The one-way sharable user model is designed to be used in dense urban areas. Vehicle Stacks will be placed throughout the city to create an urban transportation network that takes advantage of existing infrastructure such as subway and bus lines. By placing stacks in urban spaces and key points of convergence, the vehicle allows the citizens the flexibility to combine mass transit effectively with individualized mobility. The stack receives incoming vehicles and electrically charges them. Similar to luggage carts at the airport, users simply take the first fully charged vehicle at the front of the stack. The City car is NOT a replacement for personal vehicles, taxis, buses, or trucks; it is a NEW vehicle type that promotes a socially responsible and more effective means of urban mobility.