West Japan Railway plans to order four 11-car Series 273 electric multiple-units to replace the Series 381 trainsets used on Yakumo Limited Express services on the Hakubi line. This 1 067 mm gauge route runs across the main island of Honshu through the Chugoku mountains, connecting the Sanyo region on the Seto Inland Sea with the Sanin area on the Sea of Japan coast. The trains will run between Okayama, Kurashiki, Yonago, Matsue and Izumoshi, with the first unit expected to enter service early in 2024.
The 1∙5 kV DC Series 273 fleet will be the first in Japan to incorporate ‘natural’ passive tilting. Developed jointly by JR West, the Railway Technical Research Institute and Kawasaki Heavy Industries, this continuously records the location of the train and adjusts the amount of tilt according to stored route and track configuration data.
The tilt system differs from the previous ‘natural pendular tilting’ which relied on centrifugal forces to tilt the car bodies with activation of the mechanism through track-mounted transponders. Early versions of this system on Series 381, which was first introduced in 1973 on the Nagoya – Nagano route, led to passengers suffering tilt nausea, but later versions incorporated modifications that helped reduce the problem.