Your control room. When a line your trains use is blocked - a tree down, a failed train, police on the line - Control works to your contingency plan for that line: wait for it to reopen, turn trains back short of it (each ends at the last station before it and its unit starts its next working back from there), the same with buses taking passengers on, or send trains that haven't set off yet round another way. When your trains are heading for one you're asked here (and in the bell): choose, or the plan is carried out a few minutes later - sooner if a train would pass the last place it could turn back.
Your default plan
For any line without a plan of its own. Only when the line is announced as blocked for at least the minutes given - shorter blockages are waited out.
Plans for your lines
The lines your trains have run on lately. A main line with another way round might divert; a busy suburban line turn back; a long rural branch wait.
People change trains at interchanges: they allow the station's connection time and catch the next train on - and if a late arrival makes them miss it, the late company pays Delay Repay. A control room holds a departure for a few minutes for a late train bringing them. Your policy says how long for the whole company; a rule for a station overrides it there - for any of your trains, or just those off one route (0 minutes: never hold there).
Rules by station
Your timetable's connections
At each station where two or more of your routes call: which arrivals connect into which departures, and the near misses - a train leaving a minute or two before people off another could make it. Moving one of them a few minutes (Diagrams) makes the connection.
Held for connections, last 7 days
How many people made or missed their connections, station by station, is on Performance.