I took the data for this map from the Victorian Government's Open Data Portal.
This was the PTV Train Station dataset (containing the geometry and other station features) and the PTV Train Station Car Park dataset (containing the number of car parking spots per railway station).
I then used QGIS to create points from the polygons contained in the original datasets and put this into a new .csv file which was then converted to a .geojson file for uploading to Mapbox.
The first issue I encountered was that each station had multiple carparks and each one had its own field in the dataset. For instance, Laverton has four separate carparks, but they all serve the station and are all labelled 'LAVERTON'.
To solve this issue, I use the VLOOKUP tool in Excel to combine the data to create a point
The other main problem was that many railway stations were not included in the car parking dataset because they have no station carparking, creating an issue with cross-referencing the data to each station's name and location coordinates.
In the absence of an easy programming solution (any suggestions are welcome by the way), I manually transferred over each station's X and Y coordinates into the new carparking dataset.
The result of this process is the data that the map runs on. You can access and download this data in the 'Aggregated data' link below.