under one end, the other end being supported by the neighbouring car. (The end cars have two axles each). They have automatic Scharfenberg couplers at the ends; in peak hours most trains consist of two coupled units, giving a total train length of 168 meters. They have video surveillance to ensure passenger and staff security and to prevent acts of vandalism. These trains introduced air conditioning in the interior and regenerative braking to the network, increasing energy efficiency. At present, there are 105 8-car trains (840 cars). An accident involving an 8-car fourth-generation train in 2002 caused it to be scrapped, necessitated the construction of 4-car sets to relieve the shortage of trains. These 4-car units (DSB class SE-SH, also known as Litra SE) can run solo in low-traffic intervals. At present, there are 31 4-car trains (124 cars) serving the S-train network. The top speed of fourth-generation trains is , although on many parts of the network their speed is limited to to due to the limitations of the signalling system, and on the Ringbane they travel at . See also List of Copenhagen S-train stations S-Bahn List of DSB locomotives and multiple units Trams in Copenhagen References External links Official Web Site DSB website (In English) Rejsekort website for ticketing (in English) Copenhagen Tourist Card Information and sales S-train network map 2018 Byens Puls: traffic information including delays Geographical map of Copenhagen rapid transit Copenhagen Metro and S-Tog Siemens product specifications pdf Railway coaches of Denmark 1650 V DC railway electrification 1934 establishments in Denmark