By Joost Koot
In the Netherlands and many other countries it is the custom to let people leave a form of public transport before you enter it. I would argue that this is an informal institution. There tend to be no formal rules about what to do when, for example, a train or metro arrives at the station. However often it can be witnessed that the people on the platform allow the passengers to get out, before they get in. This is viewed as being polite behaviour.
While there is no formal enforcement for this informal institution, it can be argued there are forms of informal enforcement. Depending on where you do not follow the rule, and who are on the platform, forms of enforcement can range from angry looks to people actively confronting you about your behaviour.
Interestingly, in his book about how American prisons are controlled by gangs, David Skarbek argues that before gang control, prisons were governed by norms and informal institutions. Due to a massive increase in prison population and diversity of the population, this was no longer possible.
This relates to behaviour at public transport stops because especially in big cities stations can be very busy and have people from different backgrounds. On top of this, as opposed to norms in prison, the chances of running into the same people afterwards, or them recognizing you are quite small. Also the punishment for not following informal institutions is much less severe within public transport than in prison, where not following the norms might get you killed.
I would argue that the reason the norm to let people get out first can still holds is that when entering you are split into relatively small groups. The big group of people waiting tends to split into smaller groups, each waiting at one of the doors. After entering you tend to be in a carriage with the same people as that you were waiting with. The pressure of these small groups might just be enough to have people observe the norm.