Well ahead of the opening of the Gyeongbu HSR for regular service, in December 1999, of the test section, later extended to , was finished to enable trials with trains. After further design changes, the high-speed tracks were finished over a length of , with of interconnections to the conventional Gyeongbu Line, including at a short interruption at Daejeon. The high-speed section itself included of viaducts and of tunnels. Conventional line electrification was finished over the across Daegu and on to Busan, the across Daejeon, and the from Daejeon to Mokpo and Gwangju. After 12 years of construction and with a final cost of 12,737.7 billion won, the initial KTX system with the first phase of the Gyeongbu HSR went into service on April 1, 2004.