This 3 level style of train was first developed here, in NSW, during the early 1960's. They entered service as trailer cars in 1964. In spite of advice from overseas experts that it couldn't be done, a prototype all-double-decker train entered operation in 1969. 

Double-deckers are now used exclusively on CityRail's suburban and interurban network. The design concept has been copied by the Europeans & Japanese. Many people regard the "K-Sets" (shown above) as the best interurban trains in Australia.