Why do railway crossings have alarms?
Short answer
Trains are heavy and cannot stop as quickly as a road vehicle. A crossing warns people and drivers before a train arrives, giving them time to stop before the tracks.
How it works
When a train is detected, an active crossing can sound a bell and flash red lights. Some crossings also lower gates that physically block the path to the tracks.
Sound can warn someone who is not looking at the crossing, while lights provide a visual signal in places where sound may be difficult to hear. The combination of bells, lights, gates, and signs varies by crossing and by region.
Key point
When the warning starts, people should stay out even if the gates have not fully lowered. The alarm is a signal to wait in a safe place until the train has passed, not a signal that there is still time to cross.