Commuter rail would be Transilien in Paris. RER is really a lot like NYC subway, maybe express trains. It's the normal Paris subway that is weird in that its st

Commuter rail would be Transilien in Paris. RER is really a lot like NYC subway, maybe express trains. It's the normal Paris subway that is weird in that its stops are waaaay too dense. To give you some perspective: a decent cyclist with a decent bike can outrun the subway in Paris, not in NYC. In terms of frequency: RER in a station on the main branch in rush hour is around 2-3 minutes, Transilien around 15 minutes, métro can be even under 2 minutes (that's why it runs on tires and not on metal wheels).