structural:summarization
Hokkaido Shinkansen

Upon commencement of services in 2016, the maximum speed on the approximately 82 km (51 mi) dual gauge section of the Hokkaido Shinkansen (including through the Seikan Tunnel) was 140 km/h (85 mph), which was increased to 160 km/h (100 mph) by March 2019. There are approximately 50 freight trains using the dual gauge section each day, so limiting the travel of such trains to times outside of Shinkansen services is not an option. Because of this and other weather-related factors cited by JR East and JR Hokkaido, the fastest journey time between Tokyo and Shin-Hakodate-Hokuto is currently 3 hours, 57 minutes.

During the 2020-21 New Year Holiday period, certain Shinkansen services were operated at 210 km/h (130 mph) on the dual gauge section and was proposed again for the Golden Week Holiday period from 3–6 May 2021, due to fewer freight trains operating.

To achieve the full benefit of Shinkansen trains travelling on the dual gauge section at 260 km/h (160 mph) (the maximum speed proposed through the tunnel), alternatives are being considered, such as a system to automatically slow Shinkansen trains to 200 km/h (125 mph) when passing narrow-gauge trains, and/or loading freight trains onto special " Train on Train " standard-gauge trains (akin to a covered piggyback flatcar train) built to withstand the shock wave of oncoming Shinkansen trains traveling at full speed. This would enable a travel time from Tokyo to Shin-Hakodate-Hokuto of 3 hours and 45 minutes, a saving of 12 minutes on the current timetable.