NS DDZ (Full name: DubbelDekkerZonering) were built by Waggonfabrik Talbot (momentarily a part of Bombardier), De Dietrich Ferroviaire (now Alstom DDF) and Adtranz between 1992 and 1998 and are operated in the Netherlands by Nederlandse Spoorwegen (NS).

This class is a type of a power concentrated electric multiple unit and was delivered in two batches as DDM-2 and DDM-3.

These are the coaches connected to the ABv, Bv, mDDM or the locomotive.

They can seat 64 people, all on the upper deck, slightly lower than in the other coaches.

Units with an mDDM are not in service as DD-ARs anymore, as they have been refurbished into DDZs.

The modernisation transformed the coaches to modern Intercity trains.

After the modernisation of the DD-ARs, the oldest 1700 series locomotives (from 1701 to 1729) are no longer used, since all new NID trains have a mDDM powercar.

The trains went temporarily out of service on December 3, 2020, due to unexplainable shaking and noise at speeds from about 100 km/h.

[3] The cause of the shaking and noise was discovered to be worn wheels from the train's braking system; specifically, the brake pads were causing the wheels to wear unevenly and too quickly.

The trains are expected to be slowly phased back into regular use beginning on December 6, 2021.