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📘 How does a railway signal control trains?

See how track circuits, blocks, aspects, and interlockings create safe train spacing.

lessons

~10 min

to learn

🔬 Science

subject

Adults

level

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What you’ll learn

Blocks
Track circuit
Occupancy
Aspect logic
Braking distance
Switches
Fail-safe design
Cab signals
Dispatching
The complete system

Questions this course answers

What does a track circuit commonly detect?

Electrical conditions in the rails change when wheelsets shunt the circuit or continuity is lost.

Why are blocks spaced with braking distance in mind?

Safe separation requires enough distance for the worst expected train to brake.

What does an interlocking protect?

Interlocking logic prevents incompatible movements and requires switches to be locked and proved.

What is a fail-safe response to a broken rail in a conventional track circuit?

Loss of continuity should produce a restrictive condition rather than an unsafe clear indication.

What does a signal aspect communicate?

The aspect conveys what movement is permitted or expected given route and block conditions.

Grounded in trusted sources

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