Now cities are full of cars. Some families even have two or more cars. Parking is a great problem, and so is the traffic in and around the cities. Something will have to be done to change it. What will the cars of tomorrow be like? Little cars may some day take the place of today's big cars. If everyone drives little cars in the future, there will be less pollution in the air. There will also be more space for parking cars in cities, and the streets will be less crowded. Three little cars can fit in the space now needed for one car of the usual size. The little cars will cost much less to own and to drive. Driving will be safer, too. What is more, these little cars can go about 65 kilometers per hour. Little cars of the future will be fine for getting around a city, but they will not be useful for long trips. If big cars are still used along with the small ones, two sets of roads will be needed in the future. Some roads will be used for the big, fast cars, and other roads will be needed for the slower small ones. The little car's size may be   _   today's car's size.
one third of two thirds of as big as as small as