>Or simply annull all the schedules and run everything extra

True - you could. On a lightly used branch only seeing one or two trains this would work fine, but it was more common to see the staff system or register used (now ABR) if it was a dead end branch.

There are advantages of having trains running on a schedule (at least in one direction) on main track that isn't CTC or double track. First, with extra trains the dispatcher has to arrange either a meet or give right over and time against each opposing extra train, before he can authorize an additional extra train. Scheduled trains just need a clearance, and keeping all extra trains in the same direction they just need running orders. Second: If communications should fail, crews could figure out how to keep trains moving safely within the rules in many cases.

With today's TWC and DTC and GCOR, if communications fail then each train eventuallhy runs out of authority and grinds to a halt until communications aree restored. Just trying to get a new warrant during a shift change is bad enough. I wonder how well things will work under PTC?