Keiō Dōbutsuen Line

The line opened on 29 April 1964 as an access route to the Tokyo Metropolitan Tama Zoological Park, which had opened in 1958. Construction had begun only in October 1963, and the work was rushed so that the line could be ready in time for the Golden Week holidays the following spring. From the outset the route was conceived chiefly for sightseeing and leisure traffic rather than ordinary commuting, and although it has always been worked as a single track, enough land was secured from the beginning to double the line should crowds to the zoo require it.

Leisure travel dominated the line's early traffic. Near Tama-Dōbutsukōen Station stood Tama Tech, a motor-sports centre and amusement park opened in 1961 by a Honda subsidiary, and the zoo and Tama Tech together gave the branch a strong recreational character. The line's role broadened, however, as higher education arrived in the area: Meisei University opened its Hino campus in 1964, the same year the line opened, and in 1978 Chuo University began relocating to a new Tama campus nearby. The branch became a principal route to both universities, and ridership rose substantially in the late 1970s as the transfer of Chuo University's functions to Tama advanced.

The opening of competing transport in 2000 reversed that growth. In that year the Tama Toshi Monorail Line was extended to Tama-Center, running parallel to the Dōbutsuen Line, and a new monorail station, Chūō-daigaku·Meisei-daigaku, opened on the south side of Tama-Dōbutsukōen as the closest stop for the two campuses. Patronage on the Keiō branch fell sharply thereafter. The decline deepened in 2009 when Tama Tech closed after forty-eight years, removing much of the line's remaining leisure demand.

From the 2010s the Keiō company responded by developing tourist attractions of its own around Tama-Dōbutsukōen Station. The Keio Rail-Land exhibition facility inside the station, first opened in March 2000, was completely renewed and reopened on 10 October 2013 as part of the company's centenary celebrations of Keiō train and bus services, and the station gained "Keio Rail-Land" as a secondary name. In March 2018 a children's play facility, Keio Asobi-no-mori HUGHUG, opened beside the station, and the surrounding area was rebranded "Kids Park Tamadō"; a related annex followed later that year.

Motive power evolved over the decades. The small Class 220 cars used on the Dōbutsuen and Keiba-jō (racecourse) lines were withdrawn on 28 September 1969, and the first-generation 5000 series, which had also worked the branch, ran a farewell service on 1 December 1996, after which 6000 series trains took over. The 6000 series in turn ended regular operation on 13 March 2011, giving way to the 7000 series that still runs the line. From 2002 a dedicated "TAMA ZOO TRAIN" set, decorated with animal illustrations, has served the branch — first a 6000 series car, then from 2011 a 7000 series set rebranded "Tama zoo Train." One-person ("wanman") operation began on 20 October 2000, and Keiō's own ATC came into use on the line on 2 October 2011.

Today the Dōbutsuen Line is a compact, two-station shuttle worked principally by four-car 7000 series trains. For many years some trains ran through to the Keiō Main Line — and, via it, to the Toei Shinjuku Line — but the timetable revision of 13 March 2011, disrupted by the Great East Japan Earthquake, suspended these through services, and a further revision on 13 March 2021 ended scheduled through running to both the Keiō and Toei lines altogether, standardising the branch on four-car trains. The parallel monorail now runs more frequently between Takahatafudō and Tama-Dōbutsukōen, but Keiō's fares remain cheaper, and from points along the Keiō Line the Dōbutsuen Line remains the faster and cheaper way to reach the zoo.

• 1963October: construction of the line begins; the work is rushed to be ready for the following spring's Golden Week holidays.
• 196429 April: the Dōbutsuen Line opens between Takahatafudō and Tama-Dōbutsukōen as an access route to the Tama Zoological Park (open since 1958).
• 196928 September: the Class 220 cars used on the Dōbutsuen and Keiba-jō lines are withdrawn following the introduction of ATS.
• 19961 December: the first-generation 5000 series runs a farewell service on the line; 6000 series trains take over operation.
• 200020 October: one-person ("wanman") operation begins on the line. (Earlier the same year the parallel Tama Toshi Monorail Line reached Tama-Center, and the Keio Rail-Land exhibit opened on 24 March.)
• 200223 March: a 6000 series set decorated with animal illustrations enters service as the first "TAMA ZOO TRAIN."
• 2009Tama Tech, an amusement park near Tama-Dōbutsukōen Station, closes after 48 years, reducing the line's leisure traffic.
• 201113 March: the 6000 series ends regular operation and the 7000 series takes over; through services to the Toei Shinjuku Line are suspended after the Great East Japan Earthquake. ATC comes into use on 2 October.
• 201310 October: the Keio Rail-Land facility reopens after a full renewal for the centenary of Keiō train and bus services, and Tama-Dōbutsukōen gains "Keio Rail-Land" as a secondary station name.
• 2018March: the children's play facility Keio Asobi-no-mori HUGHUG opens beside Tama-Dōbutsukōen Station and the surrounding area is rebranded "Kids Park Tamadō".
• 202113 March: a timetable revision ends scheduled through services to the Keiō and Toei Shinjuku lines; line operation is standardised on four-car 7000 series trains.
• 202211 December: the line is suspended for the whole day for the replacement of the Misawa overbridge carrying it across the Kawasaki-kaidō road.