I almost never travel by train, the last time was years ago. However, recently I had to take the train from Amsterdam and it was delayed for 5 minutes. No big deal, but I was just curious how often these delays occur on the Dutch railway system. I couldn’t quickly find a historical data set with information on delays, so I decided to gather my own data.
The Dutch Railways provide an API (De NS API) that returns actual departure and delay data for a certain train station. I have written a small R script that calls this API for each of the 400 train stations in The Netherlands. This script is then scheduled to run every 10 minutes. The API returns data in XML format, the basic entity is “a departing train”. For each departing train we know its departure time, the destination, the departing train station, the type of train, the delay (if there is any), etc. So what to do with all these departing trains? Throw it all into MongoDB. Why?
- Not for any particular reason :-).
- It’s easy to install and setup on my little Ubuntu server.
- There is a nice R interface to MongoDB.
- The response structure (see picture below) from the API is not that difficult to flatten to a table, but NoSQL sounds more sexy than MySQL nowadays 🙂
I started to collect train departure data at the 4th of January, per day there are around 48.000 train departures in The Netherlands. I can see how much of them are delayed, per day, per station or per hour. Of course, since the collection started only a few days ago its hard to use these data for long-term delay rates of the Dutch railway system. But it is a start.
To present this delay information in an interactive way to others I have created an R Shiny app that queries the MongoDB database. The picture below from my Shiny app shows the delay rates per train station on the 4th of January 2016, an icy day especially in the north of the Netherlands.