Cycling here looks informal enough that newcomers assume the rules are loose, then discover otherwise at a weekend checkpoint near a station. Lights, priority at unmarked junctions and alcohol limits are all actively enforced, and the fines sit at levels that startle people who cycled elsewhere for years.
A few of the ones that catch people out: no lights after dark or in poor visibility costs €75 plus administration fees, and it applies the moment your front or rear light is missing or not working, not just when you're stopped for something else. Priority-from-right, voorrang van rechts, means unmarked intersections default to whoever's coming from your right having priority, unless shark's-teeth road markings (haaientanden) tell you otherwise — plenty of longtime residents still get this wrong outside city centers where signage thins out. The alcohol limit is the same 0.5 promille (per mille blood-alcohol) that applies to drivers, and it's enforced: a cyclist between 0.5 and 0.8 promille faces roughly €179 and a short riding ban, with fines climbing sharply from there. And holding a phone is banned the same way it is for drivers, fine included. None of this is exotic or rarely enforced — cycling checkpoints, especially near train stations and nightlife areas, actively check for lights and alcohol on weekend nights.