The Seoul Transportation Corporation No. 4000 VVVF train is a commuter-type train introduced by Seoul Transportation Corporation on Seoul Metropolitan Subway Line 4 from 1993 to 1994. Currently, 52 trains (520 cars) are registered, including 26 trains dedicated to direct current and 26 trains combined with direct current, and 45 trains (450 cars) are actually in operation. History Originally, this vehicle was introduced on 1 April 1994, along with direct operation with the Gwacheon Line and the Ansan Line . Along with this, the previously operated chopper control trains were transferred to Seoul Subway Line 2 and Seoul Subway Line 3. Technical specifications Seoul Subway Line 4, the Gwacheon Line, and the Ansan Line are using a redesigned design to fit the vehicle limits. As Seoul Transportation Corporation's first lightweight stainless steel electric train, the body was made of STS301L lightweight high-strength stainless steel to induce weight reduction. An LED display board for passenger guidance was installed on the ceiling of the cabin. Low noise and miniaturization were achieved by adopting a lightweight linear driving method for the driving part of the door. Introduction history First introduction (1993–1994) Direct current only (DC): 401 to 409 formation Combination of direct current (DC/AC): 451 to 463 units Producer: Hyundai Precision Industry, Daewoo Heavy Industries The model was first introduced in 1993 with the opening of the Yangjae - Suseo section of Seoul Subway Line 3 and through service with the Gwacheon and Ansan lines. At the time of introduction, 5 10-car, 8 6-car, and 9 DC-only 10-car units were produced and introduced at Hyundai Precision Industry Changwon Plant. 10-car 1 train (451 trains) and 8 6-car trains (456-463) travelled on Seoul Subway Line 3, and the remaining 10-car trains (452-455 trains) and 5 6-car trains were on Seoul Subway Line 3. The formation (464~468) and 9 DC-only 10-car trains (401~409) were put into Seoul Subway Line 4. Since the 1 April 1994, along with the direct operation of the Gwacheon Line and the Ansan Line, one 10-car train (451 train) and 8 six-car trains (456-463 train), which were put into Seoul Subway Line 3, were also operated on Metro Line 4 in the Seoul metropolitan area. transferred to and running. Second introduction (1994–1995) Direct current (DC) only: 410 to 426 formation Combination of direct current (DC AC): 464 to 471 formation Producer: Daewoo Heavy Industries & Construction, Hyundai Precision Industry In 1994,