One train leaves. The next train is due in 5 minutes but doesn't come for 15 because of equipment problems, a medical emergency, etc. Now there are three trainl

One train leaves. The next train is due in 5 minutes but doesn't come for 15 because of equipment problems, a medical emergency, etc. Now there are three trainloads of passengers trying to get on to that train. Some won't get on till the next train or the train after that, and the trains get more delayed as people squeeze on. In the end, people are half an hour late to work.