The Pyongyang Metro () is the rapid transit system in the North Korean capital Pyongyang. It consists of two lines: the Chollima Line, which runs north from Puhŭng Station on the banks of the Taedong River to Pulgŭnbyŏl Station, and the Hyŏksin Line, which runs from Kwangbok Station in the southwest to Ragwŏn Station in the northeast. The two lines intersect at Chŏnu Station. Daily ridership is estimated to be between 300,000 and 700,000. Structural engineering of the Metro was completed by North Korea, with rolling stock and related electronic equipment imported from China. This was later replaced with rolling stock acquired from East Germany. The Pyongyang Metro has a museum devoted to its construction and history. Construction Construction of the metro network started in 1965, and stations were opened between 1969 and 1972 by president Kim Il-sung. Most of the 16 public stations were built in the 1970s, except for the two most grandiose stations—Puhŭng and Yŏnggwang, which were constructed in 1987. According to NK News sources, construction accidents in the 1970s are alleged to have potentially killed dozens of workers. China had provided technical aid for the metro's construction, sending experts to install equipment made in China, including electrical equipment made in Xiangtan, Hunan and the escalator with vertical height of 64 m made by Shanghai Seleva. Pyongyang Metro is among the deepest metros in the world, with the track at over deep underground; the metro does not have any above-ground track segments or stations. Due to the depth of the metro and the lack of outside segments, its stations can double as bomb shelters, with blast doors in place at hallways. It takes three and a half minutes from the ground to the platform by escalator. The metro is so deep that the temperature of the platform maintains a constant all year. The Saint Petersburg Metro also claims to be the deepest, based on the average depth of all its stations. The Arsenalna station on Kyiv Metro's Sviatoshynsko-Brovarska Line is currently the deepest station in the world at . The deepest heavy rail station in the world is the Jerusalem–Yitzhak Navon railway station, located underground. The Porta Alpina railway station, located above the Gotthard Base Tunnel in Switzerland, was supposed to be underground, but the project was indefinitely shelved in 2012. The system was initially electrified at 825 volts, but lowered down to 750 volts to support