In 2006, the Qinghai-Tibet Railway was opened, which is the highest railway line in the world at up to 5,072 meters (16.640 feet) above sea level. A variant of the GE Dash 9-44CW with an output of 5,100 hp was developed for the special requirements at this high altitude. These locomotives are mainly used there in front of passenger trains, which consist of cars with pressurized cabins. These form part of a link between Beijing and Lhasa. 