sentences:  In May 1930, reduced stops allowed the schedule to be cut to six hours and the train became known as the Rotorua Limited.As part of its upgrade in status from "Express" to "Limited", it became the first passenger train in New Zealand to use the new 50-foot carriages with steel panelling and enclosed vestibules.Two observation cars with lounge chairs were trialled on the service at this time, but they did not prove successful due to the economic climate created by the Great Depression and were converted into ordinary carriages.