with one half traveling the Gäubahn Eutingen–Freudenstadt to Freudenstadt, and the other half continuing on to Rottweil. Going north, these two halves are combined in Eutingen for the trip into Stuttgart. Between the two RE-trains routes (Stuttgart-Singen and Stuttgart-Rottweil), the section between Stuttgart and Rottweil has hourly service. Regional service on the Gäubahn is provided by the Deutsche Bahn AG, which has a long-term contract for this service with the state of Baden-Württemberg until 2016. In 2004, the DB AG changed the train configuration on the route Stuttgart-Singen from the locomotive-powered trains with Silberling coaches to the new DBAG Class 425 electrical multiple unit trains, which were occasionally replaced by locomotive-powered trains of the class 146, with double-decker coaches, starting in 2006. The use of the class 425 has been greatly reduced on the Stuttgart-Singen route, but those units are still the train of choice on the Stuttgart-Rottweil/Freudenstadt route. Once a day the DB AG still uses modernized Silberling coaches and a locomotive on the trip between Stuttgart and Singen. Starting on 16 March 2009, to last until 13 June 2009, the schedules for all traffic was slightly altered. This is due to the fact that since the end of 2008, by order of the German rail authority, tilting technology was not to be used on the Gäubahn. This meant a 10-minute delay for ICE traffic, and disrupted the synchronization of long-distance, regional, and local service schedules. In addition, trains using DB Class 120 locomotives, and Swiss Federal Railway coaches, replaced 4 of the ICE trains from Stuttgart to Zurich. The section between Stuttgart and Herrenberg is integrated into the Stuttgart S-Bahn network. The S 1 service runs from Herrenberg to Stuttgart-Österfeld, where the train leaves the Gäubahn and travels underground via the Verbindungsbahn to Stuttgart Hauptbahnhof. From there, the S 1 service utilizes the Fils Valley Railway as far as Plochingen, before branching off to Kirchheim unter Teck the terminus of the S 1 route. The DBAG Class 423 is used on this route. The S-Bahn is also managed by the Deutsche Bahn AG, and runs every 30 minutes, except at rush hour during the work week, where trains are available every 15 minutes. Between Herrenberg and Eutingen (some of these trains only go to Bondorf), DB AG also runs RegionalBahn trains every hour under the week, whose schedules are synchronized with the S-Bahn trains. In addition, during the