In the early 1990s Mees left the law to return to study, his doctoral research at the University of Melbourne involving a comparison of public transport in Toronto and Melbourne, and his thesis accounted for the relative success of the former compared to the latter in the post-war period, given the otherwise physical and demographic similarities of the two cities. He gained his PhD in 1997. His thesis, which was later published under the title "A Very Public Solution" is considered an authoritative text in the field.