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# Spation-temporal analysis of public transport in urban systems.

## Introduction

similar study to cite: (Alessandretti 2016)

## Isochrones and average escape velocity

We define the isochrone at time $$t$$ as the set of point on the map that are reachable, within travel time $$t$$, with the shortest public transport trip. For instance isochrones of Paris at various time are shown in figure \ref{fig:iso}.