Train on Train
# Train on Train

"Train on Train" (トレイン・オン・トレイン, Torein on Torein) is a concept for piggybacking (that is, carrying narrow-gauge wagons on broader-gauge flatwagons) by the trainload rather than one wagon at a time.

The need arose when Japan's Hokkaido Railway Company (JR Hokkaido) was planning for standard-gauge Hokkaido Shinkansen high-speed trains to operate in the undersea Seikan Tunnel from 2016. The problem was that narrow-gauge freight trains did not operate at high speeds. Since the tunnel is 53.85 km (33.46 mi) long, incorporating slower trains into the timetable would significantly disrupt high-speed services. The solution was to mount narrow-gauge freight trains on to faster standard-gauge freight trains.

## Development

When the Hokkaido Shinkansen opened between Shin-Aomori and Shin-Hakodate in 2016, high-speed Shinkansen trains would need to share the dual gauge tracks through the Seikan Tunnel linking the main island of Honshu with Hokkaido. While in the tunnel, freight trains on the narrow-gauge 1,067 mm (3 ft 6 in) rails were limited to 110 km/h (70 mph). The "Train on Train" concept involved loading narrow-gauge KoKi 100 container wagons on to specially built standard-gauge wagons to allow operation at speeds of up to 200 km/h (120 mph). As of 2020, although the plan had not been implemented, speeds were reported as having been increased to 160 km/h (99 mph) after extensive testing.

The "Train on Train" concept was announced in 2006 and a full-size mockup vehicle was built and demonstrated at Naebo Works in 2007. The next phase was to build a prototype train for actual operation. JR Freight was developing new Class EH800 20/25 kV AC electric locomotives to haul these and other trains through the tunnel.

A "Forum 2050" presentation by JR Hokkaido in 2010 stated that using a "double traverser" arrangement would allow an entire train to be transferred to and from the Train on Train wagons in approximately 10 minutes.

