"Public transit in North America is in crisis. Ridership is down, fares are up, breakdowns more frequent, and in some cities trains are delayed because the tracks are literally on fire. Meanwhile, ride-sharing platforms like Uber and Lyft offer an alternative to standing on a crowded bus. And...

We propose a theory-inspired measure of the accessibility of a city's center: the size of the surrounding area from which it can be reached within a specific time. Using publicly-available optimal routing software, we compute these "accessibility zones" for the 109 largest American and European...