Cities are the bedrock of civilization. For millennia, they have attracted people with the promise of superior standards of living ? from better economic and educational opportunities to easier access to quality public infrastructure such as housing, healthcare, and public transport. Today, however, many cities around the world are finding it challenging to live up to this promise. With urban migration accelerating at a dizzying rate ? the United Nations projects that over two-thirds of the world's population will live in cities or urban centers by 2050 ? existing resources and services in cities are coming under increasing pressure, rendering them dysfunctional and leading to glaring inequities.

Bogotá?s TransMilenio BRT system. Image © Felipe Restrepo Acosta, CC BY-SA 4.0, via Wikimedia Commons
Cities are the bedrock of civilization. For millennia, they have attracted people with the promise of superior standards of living ? from better economic and educational opportunities to easier access to quality public infrastructure such as housing, healthcare, and public transport. Today, however, many cities around the world are finding it challenging to live up to this promise. With urban migration accelerating at a dizzying rate ? the United Nations projects that over two-thirds of the world's population will live in cities or urban centers by 2050 ? existing resources and services in cities are coming under increasing pressure, rendering them dysfunctional an...