An article in Dutch News about crowded trains around Amsterdam.
So Amsterdam, Utrecht, Haarlem and even Hoofdorp are technically different municipalities. In reality, this is not the case: People are living in de Randstand. And especially for Amsterdam, people are commuting between the city of Amsterdam and the cities around it. Trains are running at a very high frequency, basically so often that people have stopped caring about the schedule and just show up at the platform, using the trains like one would use a tram or subway or anything else that runs more frequently that every 10 minutes.