Until 2002, some Regionalbahn services were given S-Bahn numbers. Locomotive-hauled service between Hauptbahnhof and Ahrensburg was S4 (now RB 81); between Altona and Elmshorn was S5 (now RE 6 and RB 71); and, before the extension of electric services to Aumühle in 1969, the service between Bergedorf and Friedrichsruh was S6 (now RB 11 and RE 1). S3 was used for Regionalbahn services between Hauptbahnhof and Maschen and Neugraben (now RB 31 and RE 5) until the opening of the Harburg S-Bahn in 1983/1984.