Carsharing

Carsharing is often a cheap alternative to busses and trains. People who drive their car long distances will sometimes offer to give other people lifts. The advantage of this is that they can share petrol costs.
There are various websites where you can find and search for lifts, such as “Blablacar” or on bremen.de’s blackboard under the „Mitfahrgelegenheit & Carsharing” category.