Port Island Line

Planning grew out of Kobe's reclamation of Port Island. From the late 1960s, committees studying how to move people around the new offshore district settled on a guideway transit system, and through the mid-1970s four competing side-guided AGT designs were evaluated. Kobe, wanting to nurture its local industry, instead commissioned a joint development by Kawasaki Heavy Industries, Kobe Steel and Mitsubishi Heavy Industries under the name KNT (Kobe New Transit). Because national infrastructure subsidies for AGT required a public or majority-public operator, the third-sector company Kobe New Transit was established to build and run the line, and construction proceeded in step with Port Island itself.

The line opened on 5 February 1981, the day after its completion ceremony, as Japan's first practical new-transit (AGT) system and the world's first automated driverless operation. The initial route, a one-way loop from Sannomiya through Minami-kōen to Naka-kōen, linked Sannomiya with Port Island over a distance of about 6.4 km with nine stations; at opening, attendants still rode aboard the trains. Fully unattended operation was completed on 1 August 1982. The line was fitted with full-height platform screen doors at every station — the first such installation in Japan — and its alignment, with a minimum curve radius of 30 m and gradients up to 50 per mille, was designed to exploit the capabilities of AGT as it threaded between buildings and over expressways.

The opening coincided with the Kobe Port Island Exposition, known as Portopia '81, held from 20 March to 15 September 1981; for the duration of the fair the line's traffic was dominated by exposition visitors. Ridership far exceeded the original demand forecasts, and in the early weeks unfamiliarity with the new technology contributed to frequent automatic stops and departure failures that drew public criticism. The system steadied, however, carried the exposition crowds reliably, and went on to be the forerunner that spread AGT and driverless operation across Japan; after the fair it settled into its role as the islanders' everyday transport and an access route to the district's institutions.

On 17 January 1995 the Great Hanshin (Kobe) Earthquake put the entire line out of service. Although the trains themselves stopped safely with little damage, viaducts, piers and girders were badly hit, with fallen and displaced spans and liquefaction of the island's foundations; because the line is elevated throughout and uses small, millimetre-precision current collectors, and because an AGT failure of this kind had no precedent worldwide, recovery was expected to be slow. Through accelerated work the Naka-kōen–Kita-futō loop section reopened on 22 May 1995, the Kita-futō–Naka-kōen link on 5 June, and the whole line was restored on 31 July, 195 days after the quake.

As plans took shape for an airport on a new island off Port Island, the line was extended to serve it. An initial 1998 scheme envisaged a 6.7 km extension; a revised plan announced by the city in September 2000 split the works and deferred the western section, leaving a 5.4 km extension in its present form. After two service suspensions for track-switching works, the Shimin-Hiroba–Kobe Airport extension opened on 2 February 2006, ahead of Kobe Airport's own opening on 16 February; the Naka-kōen–Shimin-Hiroba section was double-tracked at the same time, rapid services began, and the fare system moved from a flat fare to a zone-distance basis.

Several stations have since been renamed. On 1 July 2011, following the relocation of the city's central hospital and the arrival of RIKEN's next-generation supercomputer "K", the stations Shimin-Byōin-mae, Sentan-Iryō-Center-mae and Port Island Minami became Minatojima, Iryō Center and K Computer Mae respectively. After the K computer was decommissioned, K Computer Mae was renamed Keisan Kagaku Center on 19 June 2021. The rapid service introduced in 2006 was discontinued in the 28 March 2016 timetable revision, and proposals to lengthen trains from their original six cars to eight, raised as ridership grew, have not been realised.

• 19815 February: the Port Island Line opens (one day after its completion ceremony on 4 February) as Japan's first practical AGT system and the world's first automated driverless operation, running a one-way loop from Sannomiya via Minami-kōen to Naka-kōen (about 6.4 km, 9 stations).
• 198120 March – 15 September: the Kobe Port Island Exposition (Portopia '81) is held; for the duration of the fair the line's traffic is dominated by exposition visitors.
• 19821 August: fully unattended (driverless) operation is completed; at opening, attendants had still ridden aboard the trains.
• 199517 January: the Great Hanshin (Kobe) Earthquake puts the entire line out of service; viaducts, piers and girders are badly damaged.
• 199522 May: the Naka-kōen–Kita-futō loop section reopens; 5 June: the Kita-futō–Naka-kōen link reopens; 31 July: the whole line is restored, 195 days after the quake.
• 20062 February: the Shimin-Hiroba–Kobe Airport extension opens, ahead of Kobe Airport's own opening on 16 February; the Naka-kōen–Shimin-Hiroba section is double-tracked, rapid services begin, and the fare moves from a flat to a zone-distance basis. The extension distance was 5.4 km per JA (EN states the line was 'extended by 4.3 km').
• 20111 July: following the central hospital's relocation and the arrival of RIKEN's 'K' supercomputer, Shimin-Byōin-mae, Sentan-Iryō-Center-mae and Port Island Minami are renamed Minatojima, Iryō Center and K Computer Mae respectively.
• 201628 March: a timetable revision discontinues the rapid service introduced in 2006 and adds morning-peak trains turning back at Sannomiya–K Computer Mae.
• 202119 June: after the K computer was decommissioned, K Computer Mae station is renamed Keisan Kagaku Center.