What's a red signal on a train?

Related questions

1. What is Warner signal?
2. What do train whistles mean?
3. How do train crossing signals work?
4. What is calling on signal?
5. When approaching a railroad crossing with flashing lights you must?
6. What activates a train signal?
7. Do trains have traffic lights?
8. What is signal overlap?
9. What is Recfm?
10. What is a shunt signal?

Tags

1. #until
2. #favorable
3. #stopping
4. #speed
5. #restricted
6. #required
7. #railroads
8. #reached
9. #signal
10. #proceed
11. #which
12. #permissive
13. #after
14. #means
15. #longer
16. #train