The class A and B double-decker multiple units are the most modern vehicles in Sydney's commuter transport system. The nickname “Waratah” stands for the heraldic flower of New South Wales. They are based on class M and were developed with the help of Hitachi. Production of the car bodies is partly carried out in China by CNR and continues in Australia by Downer.
While the older Sydney Trains sets consisted of four cars each and two sets were usually coupled together, each train now consists of eight cars. Four of them are powered on all four axles. After 78 A sets, 24 B sets were built, which have modernized interiors and electronics.