3 ms·

I think that trains can travel in both directions on the same track and the schedule keeps them from hitting each other head-on.

blibble 5y ago
scheduling hasn't been used for preventing conflicting movements since the 1830s https://en.wikipedia.org/wiki/Railway_signalling#History_of_block_signalling https://en.wikipedia.org/wiki/Railway_signalling#History_of_...
- makeitdouble 5y ago
  Isn’t way too late if the conflict is detected at signal level ? The worst will have been avoided, but at least one of the train will have to back down to the nearest junction, and depending on how packed it is they might have to back down a few more train as well. I’d assume in reality it would deadlock from there.
  - denkmoon 5y ago
    That's why they have fancy software to route incoming trains around delayed ones.
    - makeitdouble 5y ago
      I suppose it relies on some slack in the system and everything else moving as expected. Which could also be the reason why they don't want to restart a schedule at mid-day with every active train in a non standard state.
  - lmm 5y ago
    The worst case is the trains stop running for a while, which it sounds like is what they pre-emptively did?
    - makeitdouble 5y ago
      It highly varies depending on POV, but for the railways the worse could be people piling up in stations with no idea if they'll ever get a train, and people piled up in trains, with no idea when they'll ever be able to get off. Sure stopping all trains must be burning a crazy amount of money, but the above scenario would be burning the same amount of money (I assume they have refund policies or they'd be operating with no ticketing), employee sanity, and urgent care for anything that could happen during that time. I have faith in Dutch people's kindness, the same happening in Paris would be riots and physical danger for the staff if they kept the trains running.
- jrockway 5y ago
  That is not strictly true. The LIRR Main Line east of Ronkonkoma uses timetable/train order scheduling: https://en.wikipedia.org/wiki/Train_order_operation https://en.wikipedia.org/wiki/Train_order_operation What is more interesting is how they get away with this when PTC is now mandatory (a lot of special operating rules/restrictions).
  - bigDinosaur 5y ago
    It'd make sense that a line famous for being terrible around the world (in transit circles) would still use such a system.
- throwawayEuropa 5y ago
  It still sometimes is. There was a big crash in Czech republic recently, where two passenger trains (motor units) collided head on between stations. Some local routes with few trains a day, where there is no longer any track-side staff, operate in a simplified rules (there is a whole code for that). There, the train will arrive to a station and depending on a symbol in the timetable, it will either continue to the next station without any signals or permissions needed or will wait for crossing train in oposite direction (the train driver must also unlock the station office and call the dispatcher on phone in some cases). Switches are either operated by train crew or they are self-returning (one direction always go to track 1 in station, the other direction goes to track 2, and the switches can be travelled through in the oposite direction without setting them first (this is an accident on standard switches) and they return back. So, the problem was that the crossing was there on some days and wasn't on some other days, driver forgot or misread the day and the train left into oncoming train... Was a big discussion after that to do anything, even an uncertified mobile app to shout "train coming" at the driver... Otherwise Czech rep. has a very modern European rail infra, just some local branch routes run like this saving them from being cancelled completely, but the rules were simified maybe too much.
  - throwawayboise 5y ago
    There is also the token-based control of bidirectional travel on single-track, in which physical posession of a token governs permission to enter a track block. Still used in various places. https://en.wikipedia.org/wiki/Token_(railway_signalling) https://en.wikipedia.org/wiki/Token_(railway_signalling)
denkmoon 5y ago
What if they are late?
- gridspy 5y ago
  Here is a theoretical solution: Lets say there is a north-south train line that is shared. The schedule can create a number of north slots and south slots into which a train of a given speed and length can fit. A variety of different trains could fit into the same slot. If a train is late, that train is moved into a later slot. That leaves a free slot where the train was going to go. Perhaps every later train is then delayed into a later slot also. Lets call this a rippling delay. You would probably schedule some spare slots to prevent delays rippling through the entire day's schedule. Some slots might be long enough to permit several trains going in the same direction to travel (it's more efficient if 10 north trains go then 10 south trains rather than 10 north/south interleaved).

blibble 5y ago

scheduling hasn't been used for preventing conflicting movements since the 1830s https://en.wikipedia.org/wiki/Railway_signalling#History_of_block_signalling https://en.wikipedia.org/wiki/Railway_signalling#History_of_...

makeitdouble 5y ago
Isn’t way too late if the conflict is detected at signal level ? The worst will have been avoided, but at least one of the train will have to back down to the nearest junction, and depending on how packed it is they might have to back down a few more train as well. I’d assume in reality it would deadlock from there.
- denkmoon 5y ago
  That's why they have fancy software to route incoming trains around delayed ones.
  - makeitdouble 5y ago
    I suppose it relies on some slack in the system and everything else moving as expected. Which could also be the reason why they don't want to restart a schedule at mid-day with every active train in a non standard state.
- lmm 5y ago
  The worst case is the trains stop running for a while, which it sounds like is what they pre-emptively did?
  - makeitdouble 5y ago
    It highly varies depending on POV, but for the railways the worse could be people piling up in stations with no idea if they'll ever get a train, and people piled up in trains, with no idea when they'll ever be able to get off. Sure stopping all trains must be burning a crazy amount of money, but the above scenario would be burning the same amount of money (I assume they have refund policies or they'd be operating with no ticketing), employee sanity, and urgent care for anything that could happen during that time. I have faith in Dutch people's kindness, the same happening in Paris would be riots and physical danger for the staff if they kept the trains running.
jrockway 5y ago
That is not strictly true. The LIRR Main Line east of Ronkonkoma uses timetable/train order scheduling: https://en.wikipedia.org/wiki/Train_order_operation https://en.wikipedia.org/wiki/Train_order_operation What is more interesting is how they get away with this when PTC is now mandatory (a lot of special operating rules/restrictions).
- bigDinosaur 5y ago
  It'd make sense that a line famous for being terrible around the world (in transit circles) would still use such a system.
throwawayEuropa 5y ago
It still sometimes is. There was a big crash in Czech republic recently, where two passenger trains (motor units) collided head on between stations. Some local routes with few trains a day, where there is no longer any track-side staff, operate in a simplified rules (there is a whole code for that). There, the train will arrive to a station and depending on a symbol in the timetable, it will either continue to the next station without any signals or permissions needed or will wait for crossing train in oposite direction (the train driver must also unlock the station office and call the dispatcher on phone in some cases). Switches are either operated by train crew or they are self-returning (one direction always go to track 1 in station, the other direction goes to track 2, and the switches can be travelled through in the oposite direction without setting them first (this is an accident on standard switches) and they return back. So, the problem was that the crossing was there on some days and wasn't on some other days, driver forgot or misread the day and the train left into oncoming train... Was a big discussion after that to do anything, even an uncertified mobile app to shout "train coming" at the driver... Otherwise Czech rep. has a very modern European rail infra, just some local branch routes run like this saving them from being cancelled completely, but the rules were simified maybe too much.
- throwawayboise 5y ago
  There is also the token-based control of bidirectional travel on single-track, in which physical posession of a token governs permission to enter a track block. Still used in various places. https://en.wikipedia.org/wiki/Token_(railway_signalling) https://en.wikipedia.org/wiki/Token_(railway_signalling)

denkmoon 5y ago

What if they are late?

gridspy 5y ago
Here is a theoretical solution: Lets say there is a north-south train line that is shared. The schedule can create a number of north slots and south slots into which a train of a given speed and length can fit. A variety of different trains could fit into the same slot. If a train is late, that train is moved into a later slot. That leaves a free slot where the train was going to go. Perhaps every later train is then delayed into a later slot also. Lets call this a rippling delay. You would probably schedule some spare slots to prevent delays rippling through the entire day's schedule. Some slots might be long enough to permit several trains going in the same direction to travel (it's more efficient if 10 north trains go then 10 south trains rather than 10 north/south interleaved).