Signals are not traffic lights
Colors matter, but signal meaning depends on the full aspect, signal type and railroad rules.
Block signaling
Track can be divided into blocks so train movements are protected from conflicting occupancy.
Dispatcher control
Modern railroads often combine signals, centralized traffic control and dispatching systems to manage movements over long distances.
Why exact rules vary
Different railroads and territories can use different rule sets. This page is an overview, not an operating-rules manual.
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