Waited for 1h30, and finaly took the bus to Bremen Hauptbahnhof.
Standed with a sign/Direction Osnabrück/A lot of traffic and firelamps but the cars didn't stop even if there was place to park. Bad day for us.
Good spot. Next to a bus station and traffic lights for pedestrians. Cars have time to see you and have place to park.
With thumb or sign, it could work anyway ;)