Minor correction: there are two Shinkansen lines in Japan that run trains partly on shared legacy track, namely the Akita and Yamagata "mini-Shinkansens". Howev

Minor correction: there are two Shinkansen lines in Japan that run trains partly on shared legacy track, namely the Akita and Yamagata "mini-Shinkansens". However, these sections operate at normal speed, not high speed.