S5 is planned to be extended via Friedrichsdorf to Usingen, requiring electrification of the Taunusbahn line. The green light for the project was given in May 2015, with a scheduled completion date of the end of 2019. A further extension to Grävenwiesbach (Hochtaunuskreis) and Brandoberndorf has been requested by local politicians in Hochtaunuskreis, but no action is expected until 2027 as RMV funds are already committed to the purchase of rolling stock. Similar suburban railways On several regional routes without overhead contact line, S-Bahn-like traffic was already partially introduced at the time of the Frankfurter Verkehrsverbund, ie high density of traffic, continuous weekend traffic as well as trains bound through Frankfurt during the daytime and Frankfurt main station. The operators were and are the DB Regio and the Hessian State Railways (HLB), formerly the Frankfurt-Königsteiner Eisenbahn (FKE). The FVV led these lines with their own line letter (K, T and N) or as S-Bahn line (S9, S11). This affected the following routes (sorted by today's RMV line number): Königstein Railway or Königsteiner Bahn (12): Frankfurt central station - Frankfurt-Höchst - KönigsteinFrom the highest source line of the FKE. Here, starting in 1987, first as line K, with the new procurement of vehicles and adjustment of route and signaling technology dense traffic was introduced. Since 2003, all trains run continuously to Frankfurt Central Station. Soden Railway or Sodener Bahn (13): Frankfurt-Höchst - Bad SodenFrom 1979 to 1997, the Sodener Bahn was part of the S-Bahn line S3. For this purpose, the route was electrified. Due to insufficient capacity, the S-Bahn service was abandoned and the line was taken over by the FKE. It only operates as a connecting line. Taunus Railway or Taunusbahn (15): (Frankfurt central station -) Bad Homburg - Friedrichsdorf - Usingen - Grävenwiesbach (- Brandoberndorf)The Friedrichsdorf-Grävenwiesbach line, which was about to be shut down, was bought by the Verkehrsverband Hochtaunus, modernized and handed over to the FKE in 1992 for operation. Until the founding of the RMV, the line was called T. From 1999, the decommissioned part was reactivated to Brandoberndorf. The stations have S-Bahn-like standards such as high platforms (since 1992) or Zugzielanzeiger (since 2007). In rush hour, additional trains go to Frankfurt Hauptbahnhof. Bad Vilbel–Glauburg-Stockheim railway or Niddertalbahn (34): (Frankfurt central station -) Bad Vilbel - Nidderau - Glauburg-StockheimSince the completion of the modernization work in May 2008, almost all work on weekdays and about one