Station Vehicle Waiting passenger (a) (b) (c) a b c d b c d e c d e f Figure 2: Equal headway instability. a) Vehicles with a homogeneous temporal distribution, i.e. equal headways. Passengers arriving at random cause some stations to have more demand than others. b) Vehicle c is delayed after serving a busy station. This causes a longer waiting time at the next station, leading to a higher demand ahead of c . Also, vehicle d faces less demand, approaching c . c) Vehicle c is delayed even more and vehicles d and e aggregate behind it, forming a platoon. There is a separation between e and f , making it likely that f will encounter busy stations ahead of it. This configuration causes longer waiting times for passengers at stations, higher demands at each stop, and increased vehicle travel times. The average service frequency at stations is much slower for platoons than for vehicles with an equal headway [66]. 20