Railway Signalling System

flowchart TB
  n0["system<br>Railway Signalling System"]
  n1["actor<br>Train on-board systems"]
  n2["actor<br>Signaller"]
  n3["actor<br>Railway infrastructure"]
  n4["actor<br>Maintenance management system"]
  n5["actor<br>Road users and pedestrians"]
  n6["actor<br>National timetable system"]
  n0 -->|Movement authority, cab signals| n1
  n1 -->|Train position, speed, braking| n0
  n2 -->|Route requests, override commands| n0
  n0 -->|Track state display, alarms| n2
  n3 -->|Track circuit currents, point feedback| n0
  n0 -->|Fault logs, diagnostics| n4
  n0 -->|Level crossing warnings| n5
  n6 -->|Planned timetable, route schedules| n0