東急東横線
The 40000 series trains operate on Seibu Ikebukuro Line, Seibu Shinjuku Line, and Seibu Haijima Line services. Some trainsets operate on reserved-seat supplementary-fare "S-Train" services between the Seibu Ikebukuro Line and Tokyo Metro Yurakucho Line on weekdays and between the Seibu Chichibu Line and Minato Mirai Line (via the Tokyo Metro Fukutoshin Line and Tōkyū Tōyoko Line) at weekends since 25 March 2017.