due to the mausoleum of Kim Il-sung being located at that station. Trains do not stop at that station. The map of the Hyŏksin line shows two additional stations after Kwangbok: Yŏngung () and Ch'ilgol (), both of them reportedly under development. The map of the Chollima Line, on the other hand, shows four additional stations, two at each end of the line—Ryŏnmot (), Sŏp'o (), Ch'ŏngch'un () and Man'gyŏngdae ()—also planned or under development. However, the most recent maps omit these stations. The Chollima line is already connected to the State Railway Sopo station on the way to the metro depot, and plans of the metro seem to suggest that the non-commercial segment of this line would be eventually part of the metro system. However, the current tunnel exit does not allow for this, as this segment does not have third rail electrification, and is locomotive hauled by the GKD5B shunters and would require negotiating a switchback. In addition to the main system for passenger use, there is allegedly an extra system for government use, similar to Moscow's Metro-2. The secret Pyongyang system supposedly connects important government locations. There is also reportedly a massive underground plaza for mobilization, as well as an underground road connecting two metro stations. Rolling stock When operations on the Metro started in the 1970s, newly built DK4 passenger cars were used, made for North Korea by the Chinese firm Changchun Railway Vehicles. Some of the Chinese-made rolling stock have been observed operating near the Sinuiju area and northern regions. Since 1997, the Pyongyang Metro has mainly used former German rolling stock from the Berlin U-Bahn. The former Berlin trainsets were given a new red and cream livery in Pyongyang. All advertising was removed and replaced by portraits of leaders, Kim Il-sung and Kim Jong-il. In 2000, a BBC reporter saw "old East German trains complete with their original German graffiti". Koryo Tours in another article write about and show the old West-Berlin D-trains, suggesting that the BBC article could have mixing them up with the Class GI of East Berlin. After about 2006, Type D cars were mainly used. The Class GI rolling stock has been banned from underground tunnel operations due to frequent control stand fires and was withdrawn from Metro service in 2001, and those cars are now operating on the railway network around Pyongyang and northern regions as commuter trains. One