Why do trains have signals?

Related questions

1. What is a Signalling failure?
2. What is a controlled signal?
3. How many types of signals are there in railway?
4. What activates a train signal?
5. What's a red signal on a train?
6. How do automatic train signals work?
7. What do train whistles mean?
8. Do trains have red lights?
9. What is moving block system?
10. What is calling on signal?

Tags

1. #being
2. #green
3. #rather
4. #computers
5. #yellow
6. #light
7. #cautionary
8. #mechanical
9. #reliable
10. #easier
11. #began
12. #relays
13. #controlled
14. #signals
15. #trains
16. #metal
17. #control
18. #traffic
19. #1960s