a, Scatter plot showing the average total time with a passenger on board per vehicle in a day versus the total number of daily trips for that day. Each point in the scatter plot represents a day. The average total time with a passenger on board, which is a measure of vehicle utilization in the minimum fleet assignment, shows an overall increasing pattern with the increase in the number of daily trips that is consistent with the fact that the minimum fleet size shows robustness. b, Scatter plot showing the average total waiting time to pick up passengers per vehicle versus the number of daily trips for each day. The average total waiting time decreases as the number of daily trips increases, which again can be interpreted as an increase in the utilization of vehicles. The observed patterns justify the unused capacity assumption used to develop the bin-packing model (see Methods and Extended Data Fig. 6).