Engineers plan transport systems, people use them. But the ways in which an engineer measures success – speed, journey time, efficiency – are often not the way that passengers think about a good trip. We are not cargo. We choose how and when to travel, influenced not only by speed and time but by habit, status, comfort, variety – and many other factors that engineering equations don’t capture at all. As we near the practical, physical limits of speed, capacity and punctuality, the greatest...