CoolWalks for active mobility in urban street networks

TL;DR

This paper investigates how urban shading from buildings affects pedestrian walking routes, introducing a model and metric to quantify shade opportunities, revealing that street layout and building height variations influence shade-based route choices.

Contribution

It develops a route choice model with a sun avoidance parameter and introduces the CoolWalkability metric to quantify shaded walking opportunities in urban networks.

Findings

CoolWalkability is independent of sun avoidance on regular grids.

Irregular street networks offer more shade-based routing benefits.

Street geometry and building heights significantly influence shaded walking routes.

Abstract

Walking is the most sustainable form of urban mobility, but is compromised by uncomfortable or unhealthy sun exposure, which is an increasing problem due to global warming. Shade from buildings can provide cooling and protection for pedestrians, but the extent of this potential benefit is unknown. Here we explore the potential for shaded walking, using building footprints and street networks from both synthetic and real cities. We introduce a route choice model with a sun avoidance parameter $\alpha$ and define the CoolWalkability metric to measure opportunities for walking in shade. We derive analytically that on a regular grid with constant building heights, CoolWalkability is independent of $\alpha$, and that the grid provides no CoolWalkability benefit for shade-seeking individuals compared to the shortest path. However, variations in street geometry and building heights create such benefits. We further uncover that the potential for shaded routing differs between grid-like and irregular street networks, forms local clusters, and is sensitive to the mapped network geometry. Our research identifies the limitations and potential of shade for cool, active travel, and is a first step towards a rigorous understanding of shade provision for sustainable mobility in cities.