I have only seen a stop like this happen when there is another train at the station that has not cleared (or will not clear a track cross-over). The reason for

I have only seen a stop like this happen when there is another train at the station that has not cleared (or will not clear a track cross-over). The reason for a stop is announced by the conductor when the stop occurs. This happens every 30-50 trips on a busy line. I've never experienced an arbitrary stop to "maintain schedule" in the several hundred Tokyo train/subway trips I've taken. I have experienced several long slow approachs in Zurich so that the subway could arrive and stop as the second hand ticked to 12.