Some day little cars may take the place of today's cars. If everyone 1 such a little car in the future, there will be less 2 in the air. There will be more parking places in the cities, and the street will be 3. Now the space for one car of the usual size can 4 more than one such little cars. Driving will be 5, because these little cars can go only 50 kilometres an 6. The future cars will be fine for going around the city, but they will not be 7 for going far away. The little cars 8 only two batteries, one battery for the motor, and the other for the horn (汽车喇叭) and the lights. If we still 9 the big cars along with the small ones; we will need to 10 two kinds of roads. That is, there will be some roads for the big fast cars and other roads for the smaller and slower ones.