Line S3 is a line on the Munich S-Bahn network. It is operated by DB Regio Bayern. It runs from Mammendorf station to Holzkirchen station via Pasing, central Munich, Munich East, Giesing and Deisenhofen. Trains reverse in Munich East station and, in order for S-Bahn services from St Martinstraße to be inserted into the S-Bahn line while simultaneously reversing to run into the S-Bahn tunnel under central Munich or vice versa, the line between Munich East station and the flying junction between München-Giesing and Fasangarten stations is one of the few in Germany that has traffic running on the left.