In each station some trains have the green light that indicates which door side will open, but not all trains got this system and in rush hours, you really want to know which side of the train you have to be in order to leave without facing the crowd!

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This suggestion was originally created by Pedro on 2012-06-12 and has been imported from our old feedback portal at https://exploremetro.uservoice.com/forums/112459/suggestions/2919930.