A proposal presented in December 2020 by the Japan Project Industry Council (JAPIC) to transport minister Kazuyoshi Akaba estimates a multi-mode tunnel beneath the Tsugaru Strait that would complement the existing rail-only Seikan Tunnel.
Nikkei Asia states, the 2nd tunnel under the Tsugaru Strait includes two decks with the upper deck for autonomous vehicles and the lower deck for freight trains. Moreover, non-autonomous vehicles are probably to be carried on Channel Tunnel-style roll-on roll-off trains.
Almost a US$7bn budget, is expected for this tunnel, but JAPIC envisages this cost can be recouped in 32 years, assuming a 1.16% interest rate on project borrowing costs. While the first Seikan tunnel with 54km length, took 27 years to be finished in 1988, a 15 years’ period is estimated for completion of this tunnel according to geotechnical studies. Due to tweaking of the grade, depth and other factors, the second tunnel would be shorter than the first one.
The amount of the revenue which is expected from the tunnel is around US $844m per year, which fundamentally is the effect of increased agricultural shipments from Hokkaido – one of the country’s most important farming regions – and increased tourism.
According to the statements, the initial Seikan Tunnel is exposed to a 20,000 lit/min water inrush, so the new tunnel would also provide a chance for repairing the first tunnel.