When you visit a new place, traffic signs are very helpful. It's hard to imagine world without traffic signs. You may want to ask: When did people invent traffic signs?
It may sound (strange), but the first road signs were milestones (里程碑). They were used in ancient Rome. Back then, ancient Romans traveled on horseback or on foot. They placed milestones every few (kilometer). The milestones let travelers (know) how far they were from Rome.
After people invented cars, signs became more and more important. Drivers would get lost signs. As a result, Americans began to place signs on busy roads. In the 1920s, Americans (make) the first manual (说明书) for traffic signs. The book showed each sign meant. Now, different countries have different manuals.
The need for new traffic signs is always growing and changing. In the future, signs may be different, their purpose will not change. Traffic signs will still need to be able to tell people what to do on the road quickly.
