Horst was a MEP from 1970 – 1989 and from 1984 onward the Parliament’s Vice-President. When he retired he was nominated an honorary member of the EP.
From 1976 to 1980 he also was President of the German Council of the European Movement.
He repeatedly advocated a common European transport policy and the reduction of national competition rules on transport. Thus in 1989, being a transport expert, he became special adviser of the European commissioner on Transport and Travel, Karel van Miert.
Until 2006, before joining eacon, he consulted several institutions concerned with European questions on transport policy.
Horst is a trained shipping clerk.