On a busy road, the traffic can stretch for miles and miles. And that's just one road...try picturing in your head all the cars in the world! There are more than 1 billion cars out there (1,000,000,000). A million is a thousand thousands, and a billion is a thousand millions, so that's a huge number. In the U.S. alone, there are 291 million cars for just 332 million people!