Blue Line (Yokohama)

The line grew out of the "Yokohama Six Major Projects" framework announced in October 1965, which envisaged a subway as the backbone of the city's transport, linking the suburbs with the old city centre, promoting the Kōhoku New Town development, and supporting redevelopment around Sakuragichō and Kannai. On 15 July 1966 the Urban Transport Council's Report No. 9 recommended four subway lines (Lines 1–4) for the city to build, and Yokohama City Council approved the construction plan that October. Lines 1 and 3 were planned to meet and exchange trains at Kannai, which was laid out as the junction of the priority-construction sections; the formal starting point of both Line 1 and Line 3 is Kannai, although the operating origin of through services is Shōnandai.

Construction of Lines 1 and 3 began with a 1968 groundbreaking, and the first trains ran on 16 December 1972, when the 5.2 km first-phase section of Line 1 opened between Isezakichōjamachi and Kami-Ōoka with three-car 1000 series sets. The opening had slipped repeatedly: a July 1970 cloudburst flooded about 3 km of the partly built Kami-Ōoka–Yoshinochō tunnels with some 500,000 tonnes of water and silt, taking about two months to clear, and a September 1972 typhoon then flooded the nearly finished platform at Isezakichōjamachi, pushing the start from a planned spring date to December. From the outset the subway fitted automatic ticket gates at every station, a rarity in the Tokyo region at the time.

On 4 September 1976 the second phase opened: Line 1 was extended from Kami-Ōoka to Kaminagaya and from Isezakichōjamachi through Kannai to Yokohama Station, the first stretch of Line 3. From that day Line 1 and Line 3 began running through one another as a single service across Kannai, the operating pattern that still defines the line. With the completion of the Kaminagaya depot, trains were lengthened from three to five cars on 15 June 1977.

The network then grew toward Shin-Yokohama and Totsuka in stages. On 14 March 1985 the third phase opened two extensions at once — Line 3 from Yokohama to Shin-Yokohama and Line 1 from Kaminagaya to Maioka, the latter opening as a single track. Train length had been raised to six cars on 21 June 1984, the same day the air-conditioned 2000 series entered service. Line 1 reached Totsuka on 24 May 1987 as the fourth phase, though Totsuka opened only as a temporary station because work beneath the JNR lines was running late; the permanent Totsuka station opened on 27 August 1989.

The two ends were completed in the 1990s. On 18 March 1993 the fifth phase carried Line 3 the 10.9 km from Shin-Yokohama to Azamino, after the city and Tōkyū had agreed in 1984 to make Azamino — rather than Tamaplaza, which Tōkyū had pressed for — the northern terminus. The 3000 series (later 3000A) had entered service on 6 July 1992 ahead of that extension. On 29 August 1999 the sixth and final phase opened Line 1 from Totsuka to Shōnandai, bringing the line to its present 40.4 km; on the same day the intermediate "Shin-Yokohama-Kita" station was renamed Kita-Shin-Yokohama to avoid confusion with Shin-Yokohama.

Station numbering using the prefix "B" was introduced in 2002, the line's thirtieth year, alongside a 2002 FIFA World Cup tie-in that decorated each of the 32 stations for one participating nation. The Transportation Bureau settled on the combined name "Blue Line" for Lines 1 and 3 on 15 June 2006, and began using it formally on 30 March 2008 when the new Green Line opened and the two subway lines needed to be told apart. The veteran 1000 and 2000 series both ended service on 16 December 2006; driver-only (one-man) operation began on 15 December 2007 after automatic train operation had been switched on earlier that year, and platform doors were fitted at every station. Limited-stop "Rapid" services started on 18 July 2015, trimming the end-to-end journey by up to ten minutes. The fleet is now formed of 3000 series and, from 2 May 2022, 4000 series sets, and the city is planning a further 6.5 km extension of Line 3 from Azamino to Shin-Yurigaoka on the Odakyū Odawara Line.

• 196615 July: Urban Transport Council Report No. 9 recommends four subway lines (Lines 1–4) for Yokohama to build; the city council approves the construction plan on 11 October.
• 197216 December: the 5.2 km first-phase section of Line 1, Isezakichōjamachi–Kami-Ōoka, opens; three-car 1000 series sets begin revenue service.
• 19764 September: second-phase opening — Line 1 extended Kami-Ōoka–Kaminagaya, and Isezakichōjamachi–Kannai–Yokohama (the first Line 3 section) opens; through operation between Line 1 and Line 3 begins at Kannai.
• 197715 June: with the Kaminagaya depot completed, trains are lengthened from three to five cars.
• 198421 June: the 2000 series, the line's first air-conditioned trains, enters service; six-car operation begins the same day.
• 198514 March: third-phase opening — Line 3 extended Yokohama–Shin-Yokohama and Line 1 extended Kaminagaya–Maioka (the latter as a single track).
• 198724 May: fourth-phase opening — Line 1 extended Maioka–Totsuka, with Totsuka opening as a temporary station because work beneath the JNR lines was delayed.
• 198927 August: the permanent Totsuka station opens, replacing the 1987 temporary facility.
• 19926 July: the 3000 series (later designated 3000A) enters revenue service.
• 199318 March: fifth-phase opening — Line 3 extended 10.9 km from Shin-Yokohama to Azamino, the chosen northern terminus.
• 199929 August: sixth and final phase — Line 1 extended Totsuka–Shōnandai, completing the 40.4 km line; 'Shin-Yokohama-Kita' is renamed Kita-Shin-Yokohama.
• 2002Station numbering using the prefix 'B' is introduced; for the line's thirtieth year, each of the 32 stations is decorated for one nation in a 2002 FIFA World Cup tie-in.
• 200615 June: the Transportation Bureau decides on the combined name 'Blue Line' for Lines 1 and 3; the 1000 and 2000 series both end service on 16 December.
• 200715 December: driver-only (one-man) operation begins, after automatic train operation was switched on (20 January) and platform doors were installed across the line.
• 200830 March: the name 'Blue Line' comes into formal use as the Green Line opens and the two subway lines need to be distinguished.
• 201518 July: limited-stop 'Rapid' services begin, cutting the end-to-end journey by up to ten minutes.
• 20222 May: the 4000 series enters service, supplementing the 3000 series fleet.