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Thread: Priority Mission code

  1. #1
    Join Date
    Feb 2008
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    United Kingdom
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    Default Priority Mission code

    Hi hope it is possible
    I have two tracks merging into one .
    At a interlocking tower
    Both tracks have a mission code.
    Is it possible for track one to have priority over track two at the Interlocking Tower.
    When track two has set the path but is not on it.
    Track one is slightly behind by a few seconds and has to wait for track two clear.

    Hope this makes sense

    Matt

  2. #2
    Join Date
    Nov 2014
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    Thailand
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    Default

    At the moment, EIT paths are all treated as having the same priority (that may change in the future). The way that I handle such situations, using mission codes, is making use of the 'follow path' options in mission code manager:

    Let's say train A on track A (e.g. main line) should have a higher priority than train B on track B.
    - In MCM I set the follow path options for train A to be 'on path activation.' This means that paths will be requested 2 paths ahead typically.
    - For train B, I would normally set the follow path option, for the path prior to the track merge, to be 'on train entering path.' So here, the next path isn't requested until the train is on the current path. This may not be sufficient if the current path is a long one. In that case, I would set the follow path to 'none' and use a track marker, placed a little before the merging junction, to trigger the next path (you define any such triggers in the Mission Code Manager rule).

    For the above to work, all EIT path selection should be set to Manual, letting Mission Code Manager take control.

    Hope that helps,
    John

  3. #3

    Default

    Hi Matt.

    Yes that's make sense and this an enhancement wished by many EITs users. But currently there are no such priority mechanism included in EITs for merging tracks and ... it is not an easy one to implement.

    If you have a low priority train requesting a path merging some low and high priority track, there is no way for the EIT to guess that there will be soon after a conflicting request coming from a high priority train. So the low priority path activation is launched as there are no conflict at the time of the first request. And when the low priority path becomes active, if the EIT receives the high priority path request, it will then need first to cancel the low path priority and the the activate the high priority path and requeue a request for the low priority path ... THat is in fact a path preemption mechanism ... but not so easy to cancel reliably a path already granted to a train : the EIT will need to check there are enough signasl between the granted train and the granted path entry signal so that it can stops correctly (mimimum distance and minimum number of signals of 2 before the entry signal so that when the entry signal returns to EX_STOP (red) it leaves enough time and signals for the train to detect it needs to stop in time before the entry signal ...).
    So not impossible to do, but a bit touchy implementation ... As it makes sense and is wished a lot, it will probably be implemented in the future, but certainly not soon ...

    Another possible implementation would be to offer an option for low priority path to have a specified delay before starting activation process. If an higher priority path request is received during this differed delay, the high priority request will be processed before the delayed low priority request. Much more easy implementation, but will complexify the EIT user interface, that many people consider as having already a tough learning curve ...

    There is currently another method to implement a priority like between two merging tracks, use EITPathTrigger object with one EITPathTrigger placed at a low distance on the low priority track and another EITPathTrigger placed at a higher distance on the high priority merging track. This way the high priority train will request sooner its path than the low priority train giving the high priority train an advantage to obtain first its path ...
    Currently that's the only method to implement a priority like between two merging tracks.

    Hope this may help.
    Regards.
    Pierre.
    Last edited by pguy; October 16th, 2021 at 01:23 AM.

  4. #4
    Join Date
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    Default

    thanks for your help.
    Much appreciated.


    Matt

  5. #5
    Join Date
    Nov 2006
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    Wouldn't it be easier to give the high priority track a higher follow on figure?
    Track A (high priority) could be set at 6
    Track B (low priority) could be set at 3
    Therefore Track A would be set even if the approaching train was further away.


    Peter

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