Growing Urban Bicycle Networks

TL;DR

This paper analyzes the topological limitations of developing urban bicycle networks, showing that strategic, persistent investment is necessary to surpass a critical threshold for sustainable urban cycling infrastructure.

Contribution

It introduces a systematic, topological approach to model and analyze bicycle network growth, highlighting the importance of growth strategy and persistence in urban planning.

Findings

Decreasing returns on initial investments until a critical threshold

Overlaps in grown networks reflect existing infrastructure patterns

Growing networks from scratch is a minimal-data, broadly applicable method

Abstract

Cycling is a promising solution to unsustainable urban transport systems. However, prevailing bicycle network development follows a slow and piecewise process, without taking into account the structural complexity of transportation networks. Here we explore systematically the topological limitations of urban bicycle network development. For 62 cities we study different variations of growing a synthetic bicycle network between an arbitrary set of points routed on the urban street network. We find initially decreasing returns on investment until a critical threshold, posing fundamental consequences to sustainable urban planning: Cities must invest into bicycle networks with the right growth strategy, and persistently, to surpass a critical mass. We also find pronounced overlaps of synthetically grown networks in cities with well-developed existing bicycle networks, showing that our model reflects reality. Growing networks from scratch makes our approach a generally applicable starting point for sustainable urban bicycle network planning with minimal data requirements.