the saarbahn is a regional stadtbahn operating on the tram-train principle in the german state of the saarland. it consists of a core line in saarbrücken and riegelsberg operating under tram operating procedures (bostrab), connected to two lines that are operated under railway operating procedures (ebo), the lebach–völklingen railway to the north and the saarbrücken–sarreguemines railway in the south. "stadtbahn saar gmbh" is responsible for the infrastructure of the central section of line, while the outer tracks are operated by the national railway infrastructure companies, db netz ag in germany and réseau ferré de france in france. "saarbahn gmbh" is the train operating company for the whole system.