INTRO: Line 1 of Inchon Rapid Transit Corp’s network carried over 57million passengers in its first year of service. Use of some of the most up-to-date signalling equipment with ATP and ATO allows 2min headways and contributes to high levels of reliability

BYLINE: Jung-Ho Lee and Ernst Ploog*

SERVING a major port and industrial centre with 2·5million inhabitants, Line 1 of the Inchon Rapid Transit network opened for business on October 6 1999. By October 31 last year it had carried nearly 57·7 million passengers. Over the 21·9 km Gyul-hyeon - Dong-mak route with its 22 stations, traffic grew to reach over 166000 journeys a day, an increase of nearly 25% on the 133000 passengers/day recorded when the line opened.

Open at first between Bak-chon and Dong-mak, Line 1 services were running every 4 to 5min at peak times and every 8min outside the peaks. Headways as low as 2min are possible, and with 310 train services operated each weekday (282 at weekends) the theoretical capacity of the route was just over 24000 passengers/hour. Following the opening of the final Bak-chon - Gyul-hyeon section on December 7 1999, the timetable was revised to meet growing demand, and 325 services are now operated each weekday, with 289 at weekends.

Achieving reliability

With no serious incidents to report, operations were at no time suspended during Line 1’s first year in service, when trains made a total of 146191 trips covering 2620573train-km.

In addition to training staff to manage incidents effectively and restore services as soon as possible, great care has been taken to build reliability into Inchon’s new metro. Power is taken at 22·9 kV from the public supply, and converted to 1·5 kV DC for traction and 6·6 kV AC for lighting and other station applications. Both are monitored by a Scada system, and there is a dual supply from the public network to guard against the risk of local power failures. At present, we are examining the potential for reducing power consumption through precise measurement of the amount of electricity consumed each day.

A digital communications network acts as the nervous system for the metro, transmitting data for the signalling, power supply and fare collection systems along optic fibre cabling that has capacity for many thousands of channels. Train radio has been installed to allow drivers to contact the control centre and other operating personnel.

Trouble-free operation of Line 1 to date has been due in no small part to the choice of signalling, installed under a contract awarded to Siemens Transportation Systems and Samsung. Based on a fail-safe Sicas computerised interlocking, LZB700M signalling provides ATP and ATO, regulating train speed, headways, train start/stop and door opening/closing.

Microprocessor interlockings

During the early stages of construction, concerns were expressed over the choice of microprocessor-based electronic interlocking in place of traditional relay-based interlocking. Although some instability was experienced during trials before Line 1 opened to the public, the signalling proved to be reliable in revenue operation. As only 30% of maintenance staff had experience of electronic interlocking, extensive training was undertaken during the commissioning process.

The training programme stressed the importance of minimising the impact of any disruption, and of restoring regular service as soon as possible should a failure occur. Installation and commissioning was simplified by a modular configuration and simple test procedures.

The LZB700M system presents many advantages, operating on the distance-to-go principle that allows trains to run safely between 80m and 280m apart. This compares with between 210m and 410m on other Korean metros which use fixed block signalling. The ability to provide very short headways should allow service frequencies to be increased in line with passenger demand. The driver is relieved of routine tasks by the ATO and ATP functions of LZB700M.

ATO helps to ensure that services run to schedule, and that energy consumption and wear are minimised by setting the optimum train speed.

The use of optic fibre communication cabling has avoided interference from induced ’noise’, and the two out of three voting principle built into the electronic interlocking avoids the decline in reliability experienced with mechanical relays.

The signalling system is based on proven Siemens components. Sicas is the first electronic interlocking to incorporate high-performance Intel 486 processors, and its hardware and software modules can be flexibly configured to meet changing demands. In addition, Sicas interlockings can form part of automatic train control and centralised traffic control systems.

The basic Sicas interlocking comprises a workstation, a Simis interlocking computer, element interface modules and trackside equipment. More than 70 elements of a basic interlocking can be controlled using the modular Sicas system, with the variable configuration able to meet a range of requirements and control up to 600 trackside devices.

Inchon Line 1 has been equipped with FTGS remote-fed coded audio-frequency track circuits, designed to provide continuous monitoring of unoccupied sections. Data controlling train operation under ATO and ATP is transmitted inductively between track and train.

Metro innovation

In addition to its signalling, communications and power supply systems, other innovations pioneered in South Korea on Inchon Line 1 include rolling stock with IGBT-based traction drives and VVVF inverters, offering significant space and maintenance advantages.

To reduce noise and vibration, a concrete trackbed was chosen. Stations are fully equipped to assist the mobility-impaired, incorporating lifts for passengers in wheelchairs and systems to guide the visually-impaired. Metro construction has also provided the opportunity to give the citizens of Inchon exciting public spaces such as Future Square and Simcheong Plaza.

By reducing dependency on the car, Line 1 of Inchon’s metro system will produce major benefits for the environment. In this way, it forms the vanguard of a construction programme that includes a new high performance express metro between Seoul and Inchon, a new line from Inchon to Suwon and the rail link to Inchon International Airport. n

Line 1 in profile

TABLE: Length km 21·95

Number of stations 22

Journey time, Gyul-hyeon - Dong-mak 43min

Maximum speed km/h 80

Commercial average km/h 35

Minimum headway 2min

Service headway 4 min

Station dwell time 30sec

Train fleet units 25

Design capacity passengers/day 276000

Number of staff 1000

CAPTION: Three trainsets wait to enter service at the depot at the northern end of Inchon metro Line 1

CAPTION: The choice of a microprocessor-based interlocking with full ATO and ATP functions has been vindicated by a high level of operational reliability

* Jung-Ho Lee is General Engineering Director at Inchon Rapid Transit Corp, and Ernst Ploog is Project Manager, Signalling & Control Systems, for Siemens Transportation Systems