DDZ Returning In Service

Since 6 December 2021, NS started to gradually reintroduce its Class DDZ double deck sets in regular service. The first trains were IC services on the Roosendaal - Nijmegen - Zwolle line.

In late 2020, all 49 DDZ compositions have been withdrawn from regular service after the staff complained about vibrations during runs about the maximum permitted speed of 140 km/h. The withdrawal was a decision based on precaution by NS and, by the circumstances of the Corona pandemic and the related reduction in train operations, did not cause much inconvenience in the passenger transport. However, NS has informed Dutch national railway safety authority ILT about the situation.

During 2021 the 49 DDZ rakes, which are formed by three or five double deck coaches and a single deck Bo’Bo’Bo’ power car with upper deck passenger compartment and with automatic couplings, have been researched on the vibrations. The outcome was that the vibrations were caused by a combination of the tear and wear of the wheels, influencing the form of the wheels in a negative way, and tear and wear of the rails. The tear and wear of DDZ’s wheels was fast and in an unregular and non-smooth way.

A new brake system has been installed after extended testing on one DDZ train. Shoe brakes at the power cars have been replaced by disc brakes. Meanwhile DDZ trains have been equipped with a Real Time Monitoring which collects all kind of relevant technical data during running, enabling accurate intervention for maintenance. The information is sent to NS maintenance subsidiary Nedtrain. Another measure taken is to introduce a more intensive maintenance regime for the DDZ trains.

Notified Body TÜV has been involved in solving the DDZ problems and has controlled the research outcome and interpretation by NS, and has stated that they are correct. The new version of DDZ has been registered by ILT. A new authorisation of DDZ trains is not required.

DDZ compositions were originally built as DD/AR (double deck/agglo regio) trains, but were converted into IC trains, designated DDZ (Double Deck train Zoning) or NID (New Intercity Double deck train) during the modernisation between 2009 and 2014. NS has already started preparation for replacing the DDZ trains after 2026 by starting a market consultation. 

Quintus Vosman