Beginnings in state politics In 1984 Hermann was elected to the
Landtag of Baden-Württemberg for the Green Party, of which he was a member to 1988. From 1992 until 1997, Hermann served as co-chair of the Green Party in Baden-Württemberg, alongside Dagmar Dehmer (1992–1993) and Barbara Graf (1995–1997).
Member of the German Parliament, 1998–2011 In
1998, Hermann was elected to the Bundestag. He was an MP of the Bundestag until 2011. In this capacity, he served as deputy chairman of the Committee on the Environment, Nature Conservation, Building and Nuclear Safety (1998–2005), member of the Parliamentary Advisory Board on Sustainability (2005–2009) and chairman of the Committee on Transport, Building and Urban Affairs (2009–2011). He was his parliamentary group's spokesperson on environmental policy (2002–2005) and on transportation policy (2005–2009).
Return to state politics In 2011, Hermann went back to Baden-Württemberg state politics and became State Minister for Transportation of the government of Winfried Kretschmann. As one of his state's representatives at the
Bundesrat, he serves on the Committee on Transport. In the
2016 state elections, he was also re-elected into the Landtag of Baden-Württemberg. ==Other activities==