Based in Glasgow, Doherty worked for British Rail, and joined the Transport Salaried Staffs' Association (TSSA) in 1972.
He soon became chairman of his branch of the union, and then became secretary of its Glasgow and West of Scotland Political Advisory Council.
[1] In 1995, Doherty returned to the UK as a divisional secretary for the union, working at its headquarters in London.
He was elected as general secretary of the TSSA in 2004, pledging to keep it affiliated to the Labour Party and use those links to campaign on the ownership and integration of railways in the UK.
In 2018, he was appointed a trustee of the Railways Pension Scheme, on the nomination of the TSSA.