The first clip in the movie with the opening credits is also the ending clip only in reverse.
Chicago was chose as the first film in this series because after the director visited Chicago with his wife in order to meet with the Italian Consulate he was fascinated with the L train and rode it during all his free time.
This Orange Line train opened on October 31st, 1993. As of 2010 the Orange Line has 17 stations and 13 miles of track with over 55,000 weekly riders.
This is one of the last known films to feature the model series of trains shown in the film. Shortly after production the Chicago Transit Authority updated the trains to a new model.