# CItyChrone

## Introduction

Spatio temporal analysis of urban systems.

## Isochrone and average escape velocity

the OpenTripplanner library combine the schedules of public transport (in the gtfs format) and the graph of the streets (downloaded from Openstreetmap) of a city and it is able to compute for each point of the map the isochrones. In this article we consider the isochrone at time $$t$$ as the set of point of the map that are reachable within travel time $$t$$ with the best combination of walk and public transports. For instance an isochrone of Paris, $$t=30min$$, is shown in the figure below.