Takagi Ryo is a Professor in the Department of Electrical and Electronic Engineering at Kogakuin University in Tokyo. His research interests include various aspects of electric railways, especially traction power supply systems, and sometimes extend to transportation systems in general. He was a Research Fellow at the University of Birmingham in the UK from 2001 to 2006. He has written and speaks in the media extensively about railways. He has been a commentator for Japan Railway Journal since 2015.