**NS DDZ** (Full name: **DubbelDekkerZonering**) were built by Waggonfabrik Talbot (now **Bombardier Talbot**) , 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 an electric multiple unit and was delivered in two batches as DDM-2 and DDM-3.
The trains were formerly known as **NS DD-AR** (full name: **Dubbeldeksaggloregiomaterieel**)
From 2009 the NS DD-AR were modernised to transform them from Sprinter to Intercity.

These are the driving trailers at the end of the sets. Each set features them. There are 79 coaches, they are 26.89 metres long and seat entirely second class. They can seat 120 people, 64 on the upper deck, 52 on the lower deck and 4 near the doors. They also feature a toilet. The trains are numbered from 270 7001 to 270 7079.

These are the coaches connected to the ABv, Bv, mDDM or the locomotive. Each set features them, either one or two. One if with an mDDM and 2 if with a Class 1700. There are 103 coaches, they are 26.40 metres long and seat entirely second class. They can seat 140 people, 64 on the upper deck, 64 on the lower deck and 12 near the doors. The trains are numbered from 280 7201 to 280 7302, 280 7508.

280 7508, which was converted from first and second class to second class only seats 124, it was previously numbered 380 7508.

These are the coaches connected to the Bv and Bvs. All sets feature one. There are 76 coaches, they are 26.40 metres long and seat both first and second class. They have 64 first class seats and 60 second class seats, for a total of 124 seats, 56 on the upper deck, 56 on the lower deck and 12 near the doors. The first and second class seating is the same on both decks, 32 first and 24 second.

The trains are numbered from 380 7501 to 380 7507, and from 380 7509 to 380 7577.

These are the motor coaches connected to the Bv. Only 50 sets feature one. mDDMs are 21.39 metres long and seat both first and second class. There are 16 first class seats and 48 second class seats. They can seat 64 people, all on the upper deck, slightly lower than in the other coaches. There are no lower deck seats, as this is where all the electrical equipment is kept. Units with an mDDM are not in service as DD-ARs anymore, as they have been refurbished into DDZs.

They are numbered from 390 7701 to 390 7750.

A formation of Bvs + ABv + Bv + Bv + 1700 has a set number of 74xx and the last two digits are the same as the last two on the Bvs of the set. A formation of Bvs + ABv + Bv + mDDM has a set number of 78xx and the last two digits are the same as the last two on the Bvs of the set.

In 2009 NedTrain started to modernise 240, including the 50 mDDM coaches, out of 308 coaches of the DD-AR rolling stock. The other 68 coaches were intended to be taken out of service and sold or scrapped.

The modernisation transformed the coaches to modern Intercity trains.[1][2]