Terlouw continued to be active in politics and in December 1982 he was nominated as the next Secretary-General of the International Transport Forum (ITF) serving from 30 January 1983 until 15 October 1991. In October 1991 Terlouw was nominated as the next Queen's Commissioner of Gelderland serving from 1 November 1991 until 1 December 1996. Terlouw also became active in the public sector, and worked as a distinguished professor of Urbanization at the University of Amsterdam from January 1997 until January 2000. After the Senate election of 1999 Terlouw was elected as a Member of the Senate serving from 8 June 1999 until 10 June 2003 and served as a frontbencher and spokesperson for the Interior, Economic Affairs and Defence.