Variable gauge train tests were conducted in the following areas: a short circuit track test and turnout passing test at the Kokura Plant of the Kyushu Railway Company; a gauge conversion test to check switching operation; an AC-DC section-passing test; a running test for Shinkansen/conventional line through-train simulation at the Shin-Shimonoseki test depot of the West Japan Railway Company, and a main-track running test on the Nippo line to check conventional line running performance. The total number of gauge conversion occurrences was 1,558 (Fig. 1).
      Speedup tests between Nishi-Kokura and Shindenbaru were performed as main-track running tests, showing secure running stability up to a top speed of 130 km/h on a narrow gauge. In the sharp curve passing test (between Beppu and Oita), smooth running on curves up to the specified value of + 15 km/h was verified. This test clarified performance, including that of lateral pressure, at or above the specified value of the 2.5 m-wheelbase variable gauge bogie. Data that can be utilized for development of the next-generation improved bogie (such as the relationship between the lateral pressure and speed) was also obtained (Fig. 2). The total running distance on the main track in this running test was 2,786 km.
      In conjunction with the running tests, proposals were made for bogie improvement, including a structure to reduce bearing size and load, and another structure to reduce the weight of the unsprung mass, decreasing vehicle vibration and its effects on the track.
      The Association of Technical Research of Free Gauge Trains was inaugurated in August 2002, and the Railway Technical Research Institute (RTRI), a member of the association, is currently conducting research in fields including performance improvement of the variable gauge bogie.
      The variable gauge train was developed on behalf of the Japan Railway Construction Public Corporation (JRCC) under the guidance of the Ministry of Land, Infrastructure and Transport.