October 2010 on behalf of five contractor companies including Hitachi. Motorola supplied the digital radio communications system for the line. The power supply for the system is drawn from two Taiwan Power Company 161 kV supplies at three Bulk Supply Substations (BSS); one incoming line serves as the main power supply while the other serves a backup. One substation (A8) is located between Chang Gung Memorial Hospital and Linkou. The main RC structure was completed in March 2011, while civil engineering was finished at the end of October. The automatic fare collection system contract was awarded to Mercuries Data Systems (MDS) on 22 October 2010 for NT$355 million. Platform screen doors are installed at all underground stations, while elevated stations are equipped with automatic platform gates. Track A large portion (78.6%) of the route length is constructed on -wide viaducts, which is used in both dense urban districts as well as rural areas with steep slopes. The route features both single-tracked and double-tracked viaducts; single-tracked viaducts were constructed with a standard span of with mobile cranes while double-tracked viaducts were constructed using an advanced shoring technique for either or spans. A noise barrier wall is used on all viaducts, and floating track beds are used for environmentally-sensitive zones. During construction, some residents in Xinzhuang expressed concern over the 7 to 9-story high elevated track and its stability during potential earthquakes. The Bureau of High Speed Rail responded that due to a base that penetrates into the ground, the tracks could withstand earthquake shake intensity over 5 without a problem. By July 2011, the last of the line's elevated support pillars were erected and by August 2011, construction of the elevated viaducts were completed. RAIL.ONE Group provided the ballastless track system for the line. 150,000 modified bi-block type B 355 ties were delivered for the line. The first set arrived between July and December 2010, while the last set began production in March 2011. A section crossing over National Highway No. 1 employs a V-shaped support system (instead of the usual vertical supports) and began construction in July 2009. Taoyuan Airport section The airport section consists of four underground stations (, , , and the future station) and is long. Both cut-and-cover and shield tunneling were used for tunnel construction. Since shield tunnels were constructed underneath existing taxiways and the control tower area, an automatic system was integrated to monitor any