gtfs2lc

Guide: GTFS → Linked Connections

Transforms a GTFS file towards a directed acyclic graph of "connections".

A connection is the combination of a departure and its successive arrival of the same trip. Our goal is to retrieve a list of connections that is sorted by departure time, better known as a Directed Acyclic Graph. This way, routeplanning algorithms can be performed.

Use it

First, unzip your GTFS file to a place on your disk using e.g., unzip gtfs.zip /tmp

Now, we need to make sure that a couple of files are ordered in a specific fashion, not required by the GTFS spec. You can do these orderings through bash as follows:

• stop_times.txt must be ordered by trip_id and stop_sequence. You can do this using this command: { head -n 1 stop_times.txt ; tail -n +2 stop_times.txt | sort; } > stop_times2.txt ; mv stop_times2.txt stop_times.txt. Mind that the number of the columns are also not standardized by GTFS and you might need to tweak the sort command.
• trips.txt must be ordered by trip_id. You can do this using this command: { head -n 1 trips.txt ; tail -n +2 trips.txt | sort; } > trips2.txt ; mv trips2.txt trips.txt.
• calendar.txt must be ordered by service_id. You can do this using this command: { head -n 1 calendar.txt ; tail -n +2 calendar.txt | sort; } > calendar2.txt ; mv calendar2.txt calendar.txt.
• calendar_dates.txt must be ordered by service_id. You can do this using this command: { head -n 1 calendar_dates.txt ; tail -n +2 calendar_dates.txt | sort; } > calendar_dates2.txt ; mv calendar_dates2.txt calendar_dates.txt.

If you've ensured this, you can install this library using: npm install -g gtfs2lc and use it as follows:

gtfs2lc /path/to/extracted/gtfs

How it works (for contributors)

We convert stop_times.txt to a stream of connection rules. These rules need a certain explanation about on which days they are running, which can be retrieved using the trip_id in the connection rules stream.

At the same time, we process calendar_dates.txt and calendar.txt towards a binary format. It will contain a 1 for the number of days from a start date for which the service id is true.

In the final step, the connection rules are expanded towards connections by joining the days, service ids and rules.

Not yet implemented:

At this moment we've only implemented a conversion from the Stop Times to connections. However, in future work we will also implement a system for describing trips and routes, a system for transit stops and a system for transfers.

Furthermore, also frequencies.txt is not supported at this time. We hope to support this in the future though.

Authors

Pieter Colpaert - [e-mail]