For frequent trains like like loop lines and subways in major cities, you can generally expect them to arrive when scheduled. These arrive every few minutes, so

For frequent trains like like loop lines and subways in major cities, you can generally expect them to arrive when scheduled. These arrive every few minutes, so anything longer than a minute is perceived as a delay. These will be reported and apologized for. For trains like JR that run longer distances and less frequently, delays of 15-20 minutes due to accidents or weather can happen. This seems to happen once every few months or so.