Kodomonokuni Line

The corridor the line follows was not originally a passenger railway. It was laid in 1942 as a military spur for ammunition transport, branching from Nagatsuta Station on the Yokohama Line to the former Tana ammunition depot — a facility of the former Imperial Japanese Army that later became a United States military ammunition store. The hilly site of that depot would, two decades later, become the grounds of the park the line was eventually built to serve.

The Children's Land park, a children's welfare facility, opened on the former depot site in 1965, and on 28 April 1967 the Kodomonokuni Line opened as an access route to it, reusing the wartime depot spur with the support of Tokyu in converting it into a revenue line. The line at first used staff-token block working. During the planning stage there had been proposals to extend the line beyond Kodomonokuni Station northward to Tsurukawa on the Odakyu Odawara Line, and an alternative to Tamagawa-gakuen-mae on the same line, but these extension plans were rejected during the legislative deliberations over the Kodomonokuni Association Law.

In its early years the line saw direct excursion rapid services from Oimachi and group trains carrying schoolchildren on outings. The Kodomonokuni Association owned the facilities and contracted the actual operation to Tokyu. On 1 April 1987, when the Railway Business Act replaced the older Local Railway Act, this arrangement was formalised: the Association became the Class-3 railway operator and Tokyu the Class-2 operator. One-man operation of the trains began on 26 January 1989.

From about 1986 large-scale residential development along the line increased the local population and with it commuter demand. Running an ordinary railway that also served commuters, however, fell outside the purpose of the Association as a public-interest body, so on 1 August 1997 the Association transferred its Class-3 railway business to the third-sector Yokohama Minatomirai Railway, and Kodomonokuni Station became unstaffed at the same time.

Yokohama Minatomirai Railway began upgrade works from October 1997. On park-closed Mondays all but the first and last trains were suspended and replaced by buses while the work proceeded; the company rebuilt the Kodomonokuni station building, installed continuous welded rail, and added a new intermediate station, Onda, where trains could pass. The Yokohama Minatomirai Railway Y000 series entered service on 1 August 1999, and on 29 March 2000 the upgrade — which Tokyu called the line's "conversion to a commuter line" — was completed: the line began running throughout the day as an ordinary commuter railway, Onda Station opened, and the old park-closed timetable was abolished.

Today the Kodomonokuni Line runs a regular pattern timetable, typically every 20 minutes during the day and as often as every 10 minutes at peak times, with extra services during busy holiday periods such as Golden Week; no express or other premium trains operate. Its fares form a system separate from Tokyu's other lines. At Nagatsuta the line shares the Tokyu platforms rather than having its own ticket gates, and at the unstaffed Onda and Kodomonokuni stations fares are handled by automatic machines. The line now serves both visitors to Children's Land and the daily commuters of the residential districts that have grown up along it.

• 1942A military spur is laid from Nagatsuta Station on the Yokohama Line to the former Tana ammunition depot to carry ammunition; this right-of-way is later reused for the Kodomonokuni Line.
• 1965The Children's Land (Kodomonokuni) recreation park opens on the site of the former ammunition depot.
• 196728 April: the Kodomonokuni Line opens as an access route to the park, reusing the wartime depot spur; staff-token block working is used at first.
• 19802 July: the rolling stock is replaced, the original Tokyu 3000 series giving way to Tokyu 7200 series aluminium-bodied cars.
• 19871 April: with the Railway Business Act replacing the Local Railway Act, the Kodomonokuni Association becomes the Class-3 railway operator and Tokyu the Class-2 operator.
• 198926 January: one-man (driver-only) operation begins on the line.
• 19971 August: as the line's commuter role grows beyond the Association's public-interest purpose, the Kodomonokuni Association transfers its Class-3 railway business to the third-sector Yokohama Minatomirai Railway; Kodomonokuni Station becomes unstaffed.
• 1997October onward: Yokohama Minatomirai Railway begins upgrade works; from 10 November trains on park-closed Mondays are largely suspended and replaced by buses while the work proceeds.
• 19991 August: the Yokohama Minatomirai Railway Y000 series enters revenue service, the first new train built directly for the line.
• 200029 March: the upgrade Tokyu called "conversion to a commuter line" is completed; the new passing station Onda opens, the line runs all day as an ordinary commuter railway, and the old park-closed timetable is abolished.