Our research was technically right, but we had not taken into account changes in human behavior. Cars are more convenient and comfortable than walking, buses and subways — and that is why they are so popular. Make them even cheaper through ride-sharing and people are coaxed away from those other forms of transit.

This dynamic became clear in the data a few years later: On average, ride-hailing trips generated far more traffic and 69% more carbon dioxide than the trips they displaced.

We were proud of our contribution to ride-sharing but dismayed to see the results of a 2018 study that found that Uber Pool was so cheap it increased overall city travel: For every mile of personal driving it removed, it added 2.6 miles of people who otherwise would have taken another mode of transportation.