sometimes required, such as a wide-span new bridge in the nature reserve Stellmoor-Ahrensburger Tunneltal, which in the context of the planning process leads to delays and More costs resulted. Rolling stock The S-Bahn uses three-car electrical multiple units (EMUs), 447 vehicles of the following types: Type 470, built from 1959 until 1970, in service until 2002 (central carriage of type 870) Type 471, built from 1939 until 1958, in service until 2001 (central carriage of type 871) Type 472, built from 1974 until 1984, in service until 2022 (central carriage of type 473) Type 474, built from 1996 until 2007 (central carriage of type 874) Type 490, built from 2013 Single three-carriage trains are designated short trains. Units can be combined to form a full train with six carriages or a long train with nine carriages. Until 2001, the S-Bahn was one of very few suburban railway systems to offer two classes of service. A quieter and more comfortable first class was available for a 50% supplement. Only type 474 and type 490 trains are in regular service. The last remaining type 470 and type 471 trains were removed from service in 2002 and 2001 respectively and the 472 trains in 2022. The type 474 trains primarily serve lines S1, S11, S3 and S31, type 490 lines S2, S21 and S31. With the extension of the S-Bahn to Stade, new dual-system trains have been deployed. These are identical to the type 474 units but with a pantograph on the central carriage to collect 15 kV alternate current from overhead lines. With the introduction of type 474, the colour scheme of ivory and teal was replaced by a colour called "Traffic Red" (RAL 3020). External advertising covering the entire bodies of trains was abandoned at this time. The implementation of a consistent corporate design led to type 472 trains being updated with the new colour scheme. This has left the Berlin S-Bahn as the only German S-Bahn train types with an individual design. Type 474 trains were initially in the same colour scheme as the type DT4 trains of the Hamburg U-Bahn (white, grey, red). This early experiment was quickly given up. In 2013, 60 trains are ordered from Bombardier for 327 million euros. The trains are being delivered since 2016. These trains were at first, and to a lesser extent still are, notorious for their sensitive doors, making them more