sentences:  As many types of railcars are operated, class names have been given to each railcar type to differentiate them from others.In the early 20th century, NZR began investigating railcar technology to provide profitable and efficient passenger services on regional routes and rural branch lines where carriage trains were not economic and "mixed" trains (passenger carriage(s) attached to freight trains) were undesirably slow.A number of experimental railcars and railbuses were developed