The 16-car double-decker trains, set to go into operation at the end of 2015, are 400 metres long, requiring special training for drivers and technicians, according to a press report.
SBB has been conducting simulations since the beginning of the month to see how such trains would actually operate.
“We wanted to learn in reality how to overcome problems with these monsters,” SBB spokesman Reto Scharli is quoted as saying by the 20 Minutes online news site.
The Twindexx Swiss Express trains, produced by Bombardier, are capable of carrying 1,400 passengers in their longest versions.
They are part of a 1.9-billion-franc ($2 billion) order announced by the state-owned railway — the biggest in its history — to supply 59 new trains, totalling 436 carriages, with the first ones set for delivery next year.
The Twindexx trains, with a top speed of 230 kilometres per hour, are to be built in Villeneuve in the canton of Vaud and in Görlitz, Germany, while their propulsion and control systems are being produced in Västerås, Sweden.
The trains are touted for passenger comfort, their ability to negotiate curves at high speed and their energy efficiency.
SBB locomotive drivers, such as Roger Walder, expressed concerns about the longer trains because he said it will be necessary to arrive at stations more slowly than before.
“We will lose time,” Walder told 20 Minutes.
A slowdown of this kind is something that “in day-to-day practice we cannot allow," he said, adding that there are visibility issues with the new train.
The Swiss union of locomotive drivers, meanwhile, has raised concerns about the lack of a proper entrance door for the driver’s cabin.
“Drivers will have to thread their way between passenger luggage to go to work,” union president Hubert Giger told 20 Minutes.