The trains were introduced on Interregio Line IR 13/37 services from Basle to Zürich, St Gallen and Chur with the start of the 2019 timetable. However, SBB says the fleet has been dogged by technical malfunctions, resulting in delays and cancellations.

The Twindexx trains were originally due to enter service in December 2013 but did not receive a conditional Authorisation to Place in Service (APS) until December 2017. A dispute over accessibility for passengers with reduced mobility resulted in further delays to the fleet’s introduction.

“For customers and staff of SBB, the reliability of the FV-Dostos in the first month of operation was unacceptable,” SBB said in the statement. “Due to the timetable, the use of the new trains in the Rhine Valley cannot be halted.”

SBB says it is working with Bombardier to improve the operational stability of the trains, and it expects the remaining defects, including door failures and control system malfunctions “will be corrected immediately.”

The operator also says it expects Bombardier to take additional measures to improve smoothness at lower speeds.

Bombardier technicians are accompanying all trains in service and a new software version is being installed to improve door reliability.

In addition to Line IR 13/37, SBB plans to introduce the trains on Line IC 1 services from St Gallen to Geneva Airport, but says it will only expand the Twindexx fleet’s sphere of operation if the 12 trains currently available for service can operate reliably in day-to-day service. In the meantime, SBB will continue to use IC2000 and EW IV push-pull coaches on Line IC1.