Aonami Line

The corridor began life as freight infrastructure. After the national railway's Gifu construction office surveyed the route in October 1947, the Nishi-Nagoyakō Line opened on 1 June 1950 as a freight branch of the Tōkaidō Main Line, running 12.6 km from Sasashima Freight Terminal to Nishi-Nagoyakō and operated by Japanese National Railways (JNR). Steam haulage on the branch was discontinued on 25 April 1971. Nagoya Freight Terminal opened on 1 October 1980, and when Sasashima Freight Terminal was closed in the JNR timetable revision of 1 November 1986, the line's nominal starting point shifted to Nagoya Station without any change in distance.

With the division and privatisation of JNR on 1 April 1987, the line passed to the Central Japan Railway Company (JR Central) as a Class 1 railway operator, with JR Freight as a Class 2 operator running the freight trains. Plans to add passenger service took shape in the 1990s, and on 2 December 1997 the third-sector company Nagoya Rinkai Rapid Transit was established, funded by the city of Nagoya; it obtained a Class 1 railway licence ten days later. The passenger scheme reused roughly 12 km of the existing freight line and added a newly built extension of about 4 km out to Kinjō-futō Station.

The freight alignment was rebuilt for passengers over the following years. The Nagoya–Nagoya Freight Terminal section was electrified on 30 March 1998, the redundant Nagoya Freight Terminal–Nishi-Nagoyakō section was abolished in 2001, and the route was upgraded with new stations between Nagoya and Nakajima while the tracks beyond Nakajima were elevated to remove level crossings. The chosen nickname "Aonami Line" was settled by public poll on 17 November 2003, test runs began in April 2004, and construction cost in the region of 93 billion yen.

The Aonami Line opened to passengers on 6 October 2004, running 15.2 km from Nagoya to Kinjō-futō as the Nishi-Nagoyakō Line of Nagoya Rinkai Rapid Transit; on the same day JR Central's Class 1 freight operation between Nagoya and Nagoya Freight Terminal was discontinued, although JR Freight continues to work freight over the Nagoya end of the line, so the section between Nagoya and Arako carries both passenger and freight traffic. On 23 October 2008 a morning train derailed just after leaving Nagoya, suspending services in both directions until about 22:30.

Despite serving destinations such as the Nagoya International Exhibition Hall, ridership fell well short of the figures projected at opening. In July 2010 the operating company declared debts of around 46 billion yen and applied for alternative dispute resolution to avoid bankruptcy. The line later found a firmer footing as the principal rail access to new waterfront attractions clustered near its Kinjō-futō terminus.

The SCMaglev and Railway Park, JR Central's railway museum, opened nearby in 2011, and to mark the 2017 opening of Legoland Japan the operator introduced non-stop trains between Nagoya and Kinjō-futō on 10 March 2017, followed by a Legoland-themed wrapped train on 27 March. In 2022 the intermediate station Nagoya Keibajō-mae was renamed Kōhoku after the adjacent racecourse moved away. Today the Aonami Line functions chiefly as a commuter and leisure route linking central Nagoya with the port district and its exhibition, museum and theme-park destinations.

• 1947October: the JNR Gifu construction office carries out a survey for the planned freight line.
• 19501 June: the Nishi-Nagoyakō Line opens as a JNR freight branch of the Tōkaidō Main Line, Sasashima Freight Terminal–Nishi-Nagoyakō, 12.6 km.
• 197125 April: steam locomotive haulage on the branch is discontinued (de-steaming).
• 19801 October: Nagoya Freight Terminal opens on the line.
• 19861 November: Sasashima Freight Terminal is abolished in the JNR timetable revision, so the line's starting point becomes Nagoya Station (no change in distance).
• 19871 April: with the division and privatisation of JNR, JR Central becomes the Class 1 operator and JR Freight the Class 2 operator.
• 19972 December: Nagoya Rinkai Rapid Transit is established as a third-sector company funded by the city of Nagoya; it obtains a Class 1 railway licence on 12 December.
• 199830 March: the Nagoya–Nagoya Freight Terminal section is electrified.
• 200131 March: the Nagoya Freight Terminal–Nishi-Nagoyakō section (8.7 km) is abolished.
• 200317 November: the nickname 'Aonami Line' is chosen by public poll.
• 20046 October: the Aonami Line opens to passengers as the Nishi-Nagoyakō Line of Nagoya Rinkai Rapid Transit, Nagoya–Kinjō-futō, 15.2 km; JR Central's Class 1 freight operation between Nagoya and Nagoya Freight Terminal is discontinued the same day.
• 200823 October: a morning train derails just after departing Nagoya; services in both directions are suspended until about 22:30.
• 2010July: the operating company declares debts of around 46 billion yen and applies for alternative dispute resolution (ADR) to avoid bankruptcy.
• 201710 March: non-stop trains between Nagoya and Kinjō-futō begin for the opening of Legoland Japan; a Legoland-themed wrapped train follows on 27 March.
• 202212 March: the intermediate station Nagoya Keibajō-mae is renamed Kōhoku after the adjacent racecourse moves away.