Origins

The Seoul-Busan axis is Korea's main traffic corridor. In 1995, it housed 73.3% of Korea's population, and conducted 70% of the freight traffic and 66% of the passenger traffic. With both the Gyeongbu Expressway and Korail's Gyeongbu Line congested, the government saw the need of another mode of transport.^[1]

The first proposals for a second Seoul-Busan railway line originated from a study prepared between 1972 and 1974 by experts of France's SNCF and Japan Railway Technical Service on a request from the IBRD.^[1][2] A more detailed 1978-1981 study by KAIST, focusing on the needs of freight transport, also came to the conclusion that separating off long-distance passenger traffic on a high-speed passenger railway would be advisable, thus it was taken up in Korea's next Five Year Plan.^[1]

During the next years, several feasibility studies were prepared for a high-speed line with a Seoul–Busan travel time of 1 hour 30 minutes, which gave positive results.^[1] In 1989, following the go-ahead for the project, the institutions to manage its preparation were established: the Gyeongbu High Speed Electric Railway & New International Airport Committee, and the High Speed Electric Railway Planning Department (later renamed HSR Project Planning Board).^[1] In 1990, the foreseen Seoul-Busan travel time was 1 hour 51 minutes,^[1] the project was to be implemented by August 1998, and costs were estimated at 5,846.2 billion South Korean won^[1] in 1988 prices, of which 4.8 trillion won was foreseen for the high-speed line itself, and the remainder for rolling stock.^[3]

In 1991, bids were called for the supply and technology transfer of the core system technology,^[4] which in addition to the rolling stock also included the catenary and signalling of the line.^[5] On 26 August 1991,^[4] three competitors submitted bids: consortia led by GEC-Alsthom (today Alstom, one of the builders of France's TGV trains; Siemens, one of the builders of Germany's ICE trains; and Mitsubishi, one of the builders of Japan's Shinkansen trains.^[6]

Once planning progressed, in March 1992, the Korea High Speed Rail Construction Authority (KHSRCA) was established as a separate body with own budget responsible for the project.^[1] In the 1993 reappraisal of the project, the finishing date was pushed out to May 2002, and estimated costs grew to 10.74 trillion won.^[1][3] 82% of the cost increase was due to a 90% increase of unit costs in the construction sector (mostly labour costs but also material costs),^[3] the remainder due to alignment changes (longer route, more stations), though some city tunnels were dropped.^[1] To finance the project, the option of a Build-Operate-Transfer (BOT) franchise was rejected as too risky.^[3] Funding included direct government grants (35%), government (10%) and foreign (18%) loans, domestic bond sales (31%) and private capital (6%).^[3]

Start of construction

KHSRCA started construction of the Gyeongbu high-speed railway (Gyeongbu HSR) on 30 June 1992, on the 57 km (35 mi) long section from Cheonan to Daejeon, which was intended for use as test track.^[3]

Construction started before the choice of the main technology supplier, thus alignment design was set out to be compatible with all choices.^[3] Superstructure-related design specifications included a minimum curve radius of 7,000 m (22,966 ft), a maximum gradient of 1.5%, which was later increased to 2.5%,^[5] an open line cross section including two tracks with centerlines 5.0 m (16 ft 5 in) apart, and a two-track tunnel cross sectional area of 107 m² (1,152 sq ft).^[3][7] Of the planned 411 km (255 mi) line, 152.73 km (94.90 mi) would be laid on bridges, and another 138.68 km (86.17 mi) in tunnels.^[3] However, plans were changed repeatedly, in particular those for city sections, following disputes with local governments.^[3] Planned operating speed was also reduced from 350 km/h (215 mph) to the 300 km/h (185 mph) maximum of high-speed trains on the market, thus, with project variants of up to 430.7 km (267.6 mi) line length, Seoul–Busan travel times of up to 2 hours 4 minutes were projected.^[1]

Construction suffered from early quality problems. After an independent safety inspection in 1996, repairs were necessary on 190 locations, and even partial reconstruction was needed at another 39 locations.^[8]

Meanwhile, the bidding of the core system technology contract progressed through five rounds of evaluation, and the French and German consortia submitted final bids on 15 June 1993.^[4] KHSRCA announced that the GEC-Alsthom-led consortium was the preferred bidder on 20 August 1993, and the contract was signed on 14 June 1994.^[4] The consortium consisted of GEC-Alsthom and its Korean subsidiary Eukorail.^[9]

The technology was almost identical to that found on the high-speed lines of France's TGV system.^[10] Track-related design specifications included a design speed of 350 km/h (215 mph), standard gauge, continuously welded rails with UIC 60 profile (60 kg/m (120 lb/yd)), 2.6 m (8 ft 6 in) wide concrete sleepers, 35 cm (14 in) high ballast bed, swing-nose switches for high-speed passage, 25 kV/60 Hz electrification, standard French TVM 430^[11] automatic cab signalling and centralised train control.^[5][7]

First phase: Seoul–Daegu and connected upgrades

KTX network map in January 2021, with the Gyeongbu HSR in blue

Following the 1997 Asian Financial Crisis, the government decided to realise the Gyeongbu HSR in two phases.^[1] In a first phase, 222.1 km (138.0 mi) of the high-speed line would be finished by 2004, with trains travelling along the upgraded conventional line along the rest of the planned 409.8 km (254.6 mi) route.^[3] With the rest of the now 412 km (256 mi) long Gyeongbu HSR (now including 112 km (70 mi) of viaducts and 189 km (117 mi) of tunnels) finished, travel time was foreseen to be 1 hour 56 minutes.^[3] The budget for the first phase was set at 12,737.7 billion won, that for the entire project at 18,435.8 billion won in 1998 prices.^[3] While the share of government contributions remained unchanged, the share of foreign loans, domestic bond sales and private capital changed to 24%, 29% and 2%.^[3]

Well ahead of the opening of the Gyeongbu HSR for regular service, in December 1999, 34.4 km (21.4 mi) of the test section was finished to enable trials with trains.^[1] The test section extended to 57.2 km (35.5 mi) on 26 June 2000.^[12]

After further design changes, the high-speed tracks were finished over a length of 223.6 km (138.9 mi), with 15.0 km (9.3 mi) of interconnections to the conventional Gyeongbu Line, including at a short interruption at Daejeon.^[13] The high-speed section itself included 84 viaducts with a combined length of 83,078 m (51.622 mi),^[14] among them the 6,844 m (22,454 ft) Pungse Viaduct;^[15] and 46 tunnels with a combined length of 75,621 m (46.989 mi),^[14] among them the 10,290 m (33,760 ft) Iljik Tunnel and the 9,970.5 m (32,712 ft) Hwanghak Tunnel.^[16] Hwanghak Tunnel became Korea's longest bored tunnel once the line opened.^[17]

The project budget also included the electrification of the short connecting section at Daejeon and the Daegu-Busan section of the existing Gyeongbu Line, as well as the entire Honam Line from Daejeon to Mokpo.^[5] The Seoul–Busan route length was reduced from 441.7 to 408.5 km (274.5 to 253.8 mi).^[13]

The infrastructure and rolling stock were built in the framework of a technology transfer agreement between core system supplier Alstom and local companies, with Alstom's part of the project amounting to US$2.1 billion^[11] resp. €1.5 billion.^[9] Other foreign contributors included SNCF (training and supervision of infrastructure and operations),^[18] Pandrol^[10] and Vossloh (rail fastenings),^[18] and Cegelec (catenary).^[18] Their domestic partners for the infrastructure parts were LG Industrial Systems and Samsung (signalling and train control); ILJIN and LG Cable (catenary).^[3] SYSTRA^[19] and Bechtel^[20] was also involved in project management.

After 12 years of construction, service using the first phase of the Gyeongbu HSR started on 1 April 2004.^[7]

Second phase: Daegu–Busan

The Daegu–Busan section of the Gyeongbu HSR became a separate project with the July 1998 project revision, with a budget of 5,698.1 billion won, to be funded from direct government and private sources at the same ratios as for phase 1.^[1] In August 2006, the project was modified to include the downtown passages of Daejeon and Daegu, as well as additional stations along the phase 1 section at Osong, between Cheonan and Daejeon; and Gimcheon, (between Daejeon and Daegu. Consequently, the budget was increased to 7,190.0 billion won, and the government's share of the funding was increased by 5 percentage points to 50%.^[1]

Construction started in June 2002. The 128.1 km (79.6 mi) of new tracks, consisting of the 4.0 km (2.5 mi) South Daegu Interconnection,^[21] 122.8 km (76.3 mi) of high-speed tracks,^[22] and a 1.3 km (0.81 mi) low-speed section connecting into Busan station,^[21] follow a long curve to the northeast of the existing Gyeongbu Line, with new stations for Gyeongju and Ulsan built well outside of the city centres.^[23] The Seoul–Busan travel distance along the second phase route is 423.8 km (263.3 mi).^[22] The section includes 54 viaducts with a total length of 23.4 km (14.5 mi) and 38 tunnels with a total length of 74.2 km (46.1 mi).^[24] The two largest structures are the 20,323 m (66,677 ft) long Geomjeung Tunnel, under Mount Geumjeong at the Busan end of the line;^[25] and the 13,270 m long Wonhyo Tunnel,^[26] under Mount Cheonseong south-west of Ulsan, which will be the longest and second longest tunnels in Korea once the line is opened.^[17]

The original plans foresaw a second-phase opening in 2008, with new trains cruising at a top speed of 350 km/h (217 mph) cutting Seoul-Busan travel times to just 1 hours 56 minutes.^[11] However, construction was delayed, and trains with higher top speeds weren't yet available. The main cause of delay was a long dispute over the environmental impact assessment of the Wonhyo Tunnel, which passes under a wetland area.^[26][27] The dispute gained nationwide and international attention due to the repeated hunger strikes of a Buddhist nun, led to a suspension of works in 2005,^[28] and only ended with a supreme court ruling in June 2006.^[29]

For the second phase of the Gyeongbu HSR, the RHEDA 2000 ballastless track system of German manufacturer RAIL.ONE was chosen.^[30] However, construction faced quality problems concerning sleepers and fastenings.^[8] In February 2009, cracks were found on 332 newly laid concrete sleepers on the 96.9 km (60.2 mi) long section between Daegu and Ulsan, the cause of which was improper water insulation.^[31] Meanwhile, it was revealed that the Pandrol and Vossloh clips chosen for the rail fastenings were submitted to indoor tests only, omitting field tests,^[32] and the Pandrol clips saw no prior use on another high-speed line.^[8]

With the exception of the sections across Daejeon and Daegu, the second phase went into service on 1 November 2010.^[33] By that time, 4,905.7 billion won was spent out of a second phase budget, or 17,643.4 billion won out of the total.^[24]

The two sections across the urban areas of Daejeon and Daegu, altogether 40.9 km (25.4 mi), will be finished by 2014, and will reduce the Seoul–Busan travel distance to 417.5 km (259.4 mi).^[24] As of October 2010, the total cost of the second phase was estimated at 7,945.4 billion won, that for the entire project at 20,728.2 billion won.^[24]

Other connected high-speed lines

The Honam HSR branches from the Gyeongbu HSR at its newly built Osong station, and is meant to accelerate Honam KTX services to Mokpo.^[34] The first stage from Osong to Gwangju is in construction since December 2009,^[35] and is to be opened in 2014.^[36]

A branch from the existing Gyeongbu HSR near its northern end to Suseo-dong, a southeastern ward of Seoul, was in the original plans of the Honam HSR.^[34] The Suseo High-Speed Railway was announced as a separate project, on a route from a junction with the Gyeongbu HSR at Pyeongtaek to Suseo, on 30 December 2009. The goal was to complete the project by 2014.^[37]

Singyeongju station on the second phase section of the Gyeongbu HSR is to become a junction with the re-aligned Ulsan-Gyeongju-Pohang section of the Donghae Nambu Line, which is to open in 2014.^[23] On 23 April 2009, the project was approved by the government and a ground-breaking ceremony was held.^[23] In January 2010, the early completion of the Pohang branch was confirmed by the government.^[38]

On 1 September 2010, the government released a new strategic plan, with the aim to reduce travel times for 95% of Korea to under 2 hours by 2020.^[39] Longer-term plans under consideration included a branch from the Gyeongbu HSR to Jinju and further to the southern coast.^[39]

General

Regular service started on the first phase of the Gyeongbu HSR on 1 April 2004, with KTX-I trains reaching a maximum speed of 300 km/h (186 mph).^[7] In response to frequent passenger complaints regarding speeds on the video display staying just below the advertised 300 mark, operating top speed was raised to 305 km/h (190 mph) on 26 November 2008.^[40] From 2 March 2010, KTX-II (KTX-Sancheon) trains began to use the line in commercial service with the same top speed.^[41]

As of 2011, all KTX services routed along the line also use sections of connected conventional mainlines.

The first incident on the high-speed line happened on 11 February 2011, when a KTX-Sancheon train^[42] bound for Seoul from Busan derailed on a switch in the Iljik Tunnel, 500 m (1,600 ft) before Gwangmyeong station,^[43] when travelling at around 90 km/h (56 mph).^[44] No casualties were reported, only one passenger suffered slight injury, but KTX traffic was blocked until repairs for 29 hours.^[42] Preliminary investigation indicated that the accident resulted from a series of human errors,^[43] Workers had improperly repaired a point along the tracks.^[45] Investigators found that the derailment was caused by a switch malfunction triggered by a loose nut from track, and suspected that a repairman failed to tighten it during maintenance the previous night.^[43] The switch's detectors signalled a problem earlier, however, a second maintenance crew failed to find the loose nut and didn't properly communicate the fact to the control center, which then allowed the train on the track.^[43] The rail union criticised Korail's use of hired repairmen.^[43] There were no problems with the train according to the investigation.^[45]

Gyeongbu KTX

KTX trains not deviating from the Seoul–Busan corridor are operated as the Gyeongbu KTX service.^[1] When introduced in 2004, the new service cut travel time between Seoul and Busan from 4 hours 10 minutes to 2 hours 40 minutes.^[7] The Seoul–Busan travel distance was shortened from 441.7 to 408.5 km (274.5 to 253.8 mi)^[13] The fastest services made intermediate stops only in Daejeon and Daegu, other stations were served by trains with different stopping patterns. Some Gyeongbu KTX services will continue to serve the original relation after the 1 November 2010, opening of the second phase of the Gyeongbu HSR, with travel times between 2 hours 55 minutes and 3 hours.^[46]

Korail met local demands by introducing additional KTX services between Seoul and Dongdaegu in June 2007, which left the Gyeongbu HSR between Daejeon and Dongdaegu to serve Gimcheon and Gumi on the conventional line.^[47] These services were discontinued with the opening of the Gimcheon (Gumi) station on the high-speed line.^[47] New services introduced with the same timetable change leave the Gyeongbu HSR on the Seoul–Daejeon section to serve Suwon.^[46]

With the opening of the Daegu-Busan section on 1 November 2010, the fastest Seoul–Busan services, using all of the Gyeongbu HSR with intermediate stops in Daejeon and Dongdaegu only,^[48] reduced the shortest travel times by 22 minutes to 2 hours 18 minutes.^[46] From 1 December 2010, Korail added a pair of non-stop trains^[49] with a travel time of 2 hours 8 minutes.^[50] With the completion of the sections across urban Daejeon and Daegu, a further improvement of the four-stop travel time to 2 hour and 10 minutes between Seoul and Busan is expected.^[1]

The frequency of Gyeongbu HSR services was 94 daily runs when the service started in April 2004.^[13] Three and a half months later, trains running on some days of the week only were introduced, while overall frequency was reduced.^[13] Since then, total weekly train frequency was increased with every timetable change, and fluctuates between a minimum of 120 services from Tuesdays to Thursdays to a maximum of 154 services on Saturdays in the 17 January 2011 timetable.^[51]

Evolution of long-distance passenger traffic

When the project was started, initial ridership on the Gyeongbu HSR was expected to be 200,000 passengers a day.^[52] In the first estimate after the separation of the project into phases, the prediction for the first-year average daily ridership of the Gyeongbu KTX Line was 141,497, which reduced to 115,828 in the final August 2003 forecast.^[5] Actual first-year numbers were about a half of the last estimate, but rose significantly in the second and third year.^[53] In October 2010, before the opening of the Daegu–Busan section, Korail expected total KTX ridership (including Honam KTX) to rise from the then current 106,000 to 135,000 passengers a day.^[54]

Ridership/day^[53]

2004	60,717
2005	73,567
2006	82,716
2007	84,851
2008	85,685

On the short distance relation between Seoul and Cheonan, due to the short distance and the location of the KTX station outside the city, KTX gained only a very modest market share, with little effect on the overall modal share of intercity rail.^[1] On the medium-distance relation from Seoul to Daejeon, KTX gained market share mostly at the expense of normal express services on the Gyeongbu Line, and helped to increase the total share of rail to a third.^[1] On the long-distance relations from Seoul to Daegu and Busan, KTX took both the majority of the market and the bulk of rail passengers,^[1] increasing the total share of rail from around two-fifths to a market dominating two-thirds by 2008.^[55]

Evolution of modal shares on selected relations with Gyeongbu KTX service

Gyeongbu KTX stops

The terminal for most Gyeongbu KTX services is Seoul Station, but some trains continue beyond Seoul Station for 14.9 km (9.3 mi) along the Gyeongui Line to terminate at Haengsin station,^[56] a stop added due to the station's vicinity to the main KTX maintenance facility, Goyang depot.^[57]

station (Hangul, Hanja)	Connecting lines and services	station distance	Travel distance[22]	Location
Haengsin station (행신, 幸信) (some trains)	Honam KTX Gyeongui Line	-	-14.9 km	Goyang-si, Gyeonggi-do
Seoul (서울, 서울)	Gyeongbu Line Gyeongui Line Gyeongin Line Seoul Subway Line 1 Seoul Subway Line 4 AREX	14.9 km	0.0 km	Jung-gu, Seoul-teukbyeolsi
Gwangmyeong (광명, 光明)	Honam KTX Gwangmyeong Line (Seoul Subway Line 1)	22.0 km	22.0 km	Gwangmyeong-si, Gyeonggi-do
Cheonan-Asan (천안아산, 天安牙山)	Honam KTX Janghang Line	74.0 km	96.0 km	Asan-si, Chungcheongnam-do
Osong (오송, 五松)	Honam KTX Chungbuk Line	28.6 km	124.6 km	Cheongju-si, Chungcheongbuk-do
Daejeon (대전, 大田)	Gyeongbu Line Daejeon Line Daejeon Subway Line 1	35.2 km	159.8 km	Dong-gu, Daejeon-gwangyeoksi
Gimcheon (Gumi) (김천(구미), 金泉(龜尾))	-	73.8 km	233.6 km	Gimcheon-si, Gyeongsangbuk-do
Dongdaegu (동대구, 東大邱)	Gyeongbu Line Daegu Line Daegu Subway Line 1	53.1 km	286.7 km	Dong-gu, Daegu-gwangyeoksi
Gyeongju (경주, 慶州)	-	49.0 km	335.7 km	Gyeongju-si, Gyeongsangbuk-do
Ulsan (울산, 蔚山)	-	30.0 km	365.7 km	Ulju-gun, Ulsan-gwangyeoksi
Busan (부산, 釜山)	Gyeongbu Line Busan Subway Line 1	51.7 km	417.4 km	Dong-gu, Busan-gwangyeoksi
Services using the conventional Gyeongbu Line beyond Dongdaegu
Gyeongsan (경산, 慶山)	Gyeongbu Line	12.3 km	299 km	Gyeongsan-si, Gyeongsangbuk-do
Miryang (밀양, 密陽)	Gyeongbu Line	43.0 km	342 km	Miryang-si, Gyeongsangnam-do
Gupo (구포, 龜浦)	Gyeongbu Line Busan Subway Line 3	43.6 km	385.6 km	Buk-gu, Busan-gwangyeoksi
Busan (부산, 釜山)	Gyeongbu Line Busan Subway Line 1	16.5 km	402.1 km	Dong-gu, Busan-gwangyeoksi

Passenger surveys in the first months found that the limited capacity of bus connections^[58] and the lack of subway connections for intermediate stations, especially the newly built stations Gwangmyeong and Cheonan-Asan, was the problem mentioned most often.^[5] A better connection to Cheonan-Asan station was provided by an extension of Seoul Subway Line 1 along the Janghang Line, opened on 14 December 2008.^[59] Gwangmyeong station was linked to the same subway line by a shuttle service on 15 December 2006, but it made little impact^[60] due to the longtime differences between KTX and subway train schedules.^[61]

Other services

Services using the Gyeongbu HSR only from Seoul to Daejeon and continuing all along the Honam Line are operated as the Honam KTX service.^[1] When introduced in 2004, the new service cut travel time between Yongsan in Seoul and Mokpo from 4 hours 42 minutes to 2 hours 58 minutes.^[7] From April 2011, the new Jeolla KTX service will use the same section of the Gyeongbu HSR to reach Yeosu along the Honam and Jeolla Lines, reducing the Seoul–Yeosu travel time from the current 5 hours 13 minutes to 2 hours 55 minutes.^[62] The new service will^[62] After the completion of the first stage of the Honam HSR and then the Suseo HSR, most Honam and Jeolla KTX services will use the Gyeongbu HSR only between the junction near Pyeongtaek and Osong.

Services using the Gyeongbu HSR between Seoul and Dongdaegu, and diverging to the Gyeongbu Line to reach the Gyeongjeon Line, are operated as the Gyeongjeon KTX service, which started on 15 December 2010,^[63] initially reaching Masan with a minimum travel time of 2 hours 54 minutes.^[64] This service is to be extended to Jinju by 2012.^[37]

From 2012, Korail plans to extend some KTX services to Incheon International Airport on the AREX line.^[39] The planned travel time between Incheon International Airport and Busan is 2 hours 41 minutes.^[65]

From 2015, a KTX service between Seoul and Pohang, diverging from the Gyeongbu HSR to the Donghae Line at Singyeongju station, is planned to cut travel time by 33 minutes to 1 hour 50 minutes.^[66]

Test runs

The section from Cheonan to Daejeon, with Osong depot as operations base, was used for the commissioning of the KTX-I trains before the start of regular service. Following the start of regular service, test runs were concentrated into the night hours when no regular trains ran. At 1:24 am on 16 December 2004, the experimental train HSR-350x achieved the South Korean rail speed record of 352.4 km/h (219.0 mph) on the line.^[67]