Line S4 is a line on the Munich S-Bahn network. It is operated by DB Regio Bayern. It runs from Geltendorf station to Ebersberg station via Pasing, central Munich, Munich East and Grafing station. The line is operated at 20 minute intervals between Grafrath or Buchenau and Grafing station. Two out of three trains an hour continue from Buchenau to Geltendorf and from Grafing station to Ebersberg, so that the gap between trains alternates between 20 and 40 minutes. It is operated using class 423 four-car electrical multiple units, usually as two coupled sets. In the evenings and on Sundays they generally run as single sets.