In future cities, cars are like planes that can fly high in the sky, ships that can sail freely in the ocean, submarines that can go deep into the sea.
What they need as fuel is solar energy. During daytime, they could use and store solar energy simultaneously. After sunset, they could use the stored energy to drive on, creating less pollution and protecting the environment.
When we don't need it, we can turn it into a car key and put it into our pocket. Thus, we no long need to bother to build extra parking lots which take up precious lands.
With auto rule-obeying system, the car could automatically sense the speed limit and right track around the area,rather than whichever way the driver wants to go, for the car will prevent this from happening. In this way, car accidents can be reduced greatly.