Information which carriage is at what exit

[vikiawv]

Include data on which carriage is close to what exit.

The idea emerged from a user in this discussion: https://codeberg.org/comaps/comaps/issues/2879
I have refined his idea to include sort of a prototype on what could be done. (I however have very basic knowledge only of GTFS) - There is a Libreoffice Calc document linked at the discussion as demo purpose if you want to take a look at it ;)

For now it is this basic idea:
CarriageNumber;Exitname;Stationexits;(Lines to change[optional direction])
Example: A;Stubenring;Stubenring,Dr. Karl Lueger Platz;(2,2A,74A)
For real use it probably needs to include more data about the line, line direction….

However two problems remain unsolved: What if it is a shorter train than usual? What if the train gets turned around at a stop not listed in the Lines destinations - can it then identify that it still is within the same direction.

If this data is not submitted by the PTA it is the idea that this data could be community created as sort of add-on for regular GTFS data.

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Is this all feasible within GTFS and does it follow the projects directions?

[felixguendling]

I think the usual way to do this is to have:

• formation information
• information about the platform sections
• pathways / OSM network modelling the stop

The information you would like to display in CoMaps can be derived by combining the three sources above.

To enable this in GTFS, we would need:

• Platform sections would be a third stop layer (station -> stop/track -> section). So we need to move from a two-level hierarchy to something with more levels. Doesn't have to be via stops.txt, could be a new file to keep things downward compatible.
• Formation information about trips (which would also solve other issues with portion working).

[gcamp]

I have been thinking about this lately (good timing on this issue!), and this is what I came up with : https://gist.github.com/gcamp/f6adda87793f9e7e6f8d9da36ef7584b

This is not final in any way. http://bit.ly/gtfs-vehicles also had a version of this, a much more complete but also much more complex version.

[vikiawv]

I currently think of how carriages would be solved at stops where two lines intersect at the same plattform.
This means in one direction the carriage of the first train can be overwritten by the second train.
(For example at Stop "Längenfeldgasse" in Vienna, changing from U4 towards Heiligenstadt to U6 towards Floridsdorf. But this stop also has the problem that both Lines have different amount of carriages, U4 (6) and U6 (12).)
Two pictures for Demonstration: https://commons.wikimedia.org/wiki/File:U_L%C3%A4ngenfeldgasse6.JPG and https://commons.wikimedia.org/wiki/File:I09_508_Bf_L%C3%A4ngenfeldgasse,_ET_2618,_3813.jpg (to compare the carriage diffrences)

In the other direction however, the ideal carriage on the first train would be at the exit where the ideal carriage of the next train on the other plattform is closest.

Secondly if the train runs occasionally with shorter cars than usual (for example possible in Berlin) the carriage info could be completely off.

Till now I haven't had an good Idea for solving these two problems. But I am curious if you got some ideas for solving them ;)

[jfabi]

@gcamp, I like your simplified approach toward modelling some of these aspects. Two suggests I might add:

• Addition of direction_id to both files. This should largely meet the functionality of the various orientation/direction fields that had been proposed in GTFS-VehicleBoardings—allowing the file to work for single-track (bidirectional) operations.
• To account for different vehicle lengths operating on a route, per @vikiawv's original cases, carriage_count could be part of the primary key for carriage_positions.txt.

I'm trying to think through how accessibility considerations could also be handled, say in the case where for a certain transfer, Carriage 1/8 is physically closest, however those riders needing step-free access need to use the elevator located next to Carriage 5/8. Perhaps a simple approach could incorporate facility_type or a wheelchair_accessible-like field in conjunction with to_stop_id.