 The 5-car trains were proven to easily exceed speed limits as they were some 22,500 pounds lighter than their 6-car sisters.Additionally, until the late 1980s when the Mark VI was introduced, the Resort Line was limited to 5-car trains.The stations at the Contemporary Resort and Polynesian Village were too short to accommodate a 201-foot 6-car train and had to be extended before the launch of the Mark VI.