Cars are lots of fun, dangerous. We have to be careful when we drive them or ride in them. It ’ s always a good idea to put on your seat belt when you ’ re in a car. Why? Think about this example : You put an egg on a skateboard( 滑板 ) and give it a push. If the skateboard hits a stone, it will stop, but the egg won ’ t. It will fly through the air, hit the ground and break. Now, think what would happen if you tied the egg to the skateboard. When the skateboard hits a stone, the egg won’t go flying. It will stay safely on the skateboard. Volvo, a famous Swedish carmaker, was the first to use seat belts in 1 949.Air bags are also very important for car safety because sometimes a seat belt isn’t enough. If the car is going really fast and runs into something, seat belts could even hurt the people who wear them. Most newer cars have air bags in front of and next to the seats. When a car hits something, its airbags will come out quickly in less than one second—to keep the people inside safe.