Isochrone maps depict the spatial distribution of road networks, paths and trails in such a way that highlights travelling time thresholds from one specific point.
In fact the word isochrone comes from the greek terms ísos, equal, and khrónos, time. Isochrone maps are widely used in urban planning and transportation planning to understand the time topology of a city.
This map represents the isochrone map of Trento (Italy) where the main train station (7) has been chosen as the starting point.
Due to the hilly / mountainous orography of the region, altitudes do matter in the computation of travelling times. In order to take account of this important factor, Tobler's hiking function has been used in the script.
The network given by the streets, downloaded from OpenStreetMap with the OSMnx library, have been doubled, and made directional (one opposite to the other): each edge had then the information about the heights of the starting point and the ending point, which led to the average travel time given by the hiking function.
Also, by using the informations contained in the GTFS files from Trentino Trasporti a network was created, and merged with the geographical common points of the street network. The sum of travelling times from the walking network and the transit network have been computed and represented on the map by the means of a color heatmap.