The
Shiosai service was introduced from 10 March 1975 following the completion of electrification of the
Sōbu Main Line in October 1974, using 9-car
183 series EMUs, replacing five of the seven daily diesel-powered express services that operated between / and . From the start of the November 1982 timetable revision, further 183 series EMUs were drafted in, displaced from
Toki limited express services following the opening of the
Joetsu Shinkansen, and the remaining
Inubō express services were discontinued and absorbed into the
Shiosai services, giving seven return workings daily. From the start of the 14 March 2015 timetable revision, all
Shiosai services started and terminated at Tokyo Station, with no services operating from Shinjuku. From the start of the 16 March 2024 timetable revision,
E259 series 6-car EMUs used on
Narita Express services are scheduled to also be used on Shiosai services for six return trips. Meanwhile,
E257 series trains in 5-car formations will continue to be used for one return trip. As a result, 255 series sets will no longer operate on these services. ==See also==