“Allegra”, what is a greeting phrase in the Rhaeto-Romance language, denotes electric multiple units developed by Stadler for the Rhaetian Railway. Even though they were designed to meet very hard requirements, they even exceed the specifications by a considerable margin. The main batch of 15 sets was built for the steep mountain passes of the RhB.

Since the Bernina line is being operated at 1,000 Volts DC instead of the 11,000 Volts AC used on the rest of the RhB network, the trains had to be capable to be used under both systems. To haul up to seven additional passenger cars or even freight cars on gradients of up to seven percent, Stadler installed eight traction motors instead of four as specified. This led to the designation ABe 8/12 and a continuous output of 2,320 kW (3,110 hp). When operated in the AC network, they can even deliver up to 2,800 kW (3,755 hp) for a limited time.

For flatter lines with more passengers, Stadler also delivered five four-car units called ABe 4/16. As with the ABe 8/12, Stadler installed four instead of two traction motors. So one end car is similar to one of the two powered end cars of the ABe 8/12, while the other one is just an unpowered control car. Since they are not used on the Bernina line, they only have the equipment for the AC network. They were complemented by the much larger number of the newer “Capricorn” sets, which are also called ABe 4/16 due to their general layout.