The current Baden-Baden station was originally called Oos, between 1906 and the closure of the old Baden-Baden town station in 1977 it was called Baden-Oos and then it received its current name. As part of the construction of the Karlsruhe–Basel high-speed railway, it was planned in 1990 to upgrade the railway between Karlsruhe and Offenburg for continuous operations at 160 km/h. Under a German-Swiss convention, the entire line was supposed to be converted to at least four lines by 2008, so that it could serve as the main northern approach route to the new Gotthard Base Tunnel line to Italy. As a result, Deutsche Bahn is building a high-speed line from Karlsruhe to Basel, including new and upgraded sections. Between Karlsruhe and Rastatt two lines run relatively near each other, effectively providing four tracks. The double-track section between Rastatt station and Rastatt-Niederbühl is to be increased to four lines with the construction of the Rastatt Tunnel. Between Rastatt-Niederbühl and Offenburg, two new high-speed tracks have been completed next to the old double-track line. A new section of line from Schliengen to Haltingen between Freiburg and Basel, including the 9385 metre-long Katzenberg Tunnel, was opened on 9 December 2012 to avoid a narrow, winding section between the Rhine and the Isteiner Klotz hills. The remaining sections between Offenburg, Freiburg and the Katzenberg Tunnel are still being planned. The Rhine Valley Railway is now one of the most important lines of Germany both for passenger and goods traffic, including international traffic to and from Switzerland and France. An investigation by the Hochschule Kehl (a school of public administration) estimated the traffic to be up to 286 trains a day. The line is overloaded and was considered to have an occupancy rate of 126 percent in 2011. Trains have to run at especially close intervals. All long-distance services stop at Mannheim, Heidelberg, Karlsruhe, Freiburg and Basel Bad Bf, some stop at Wiesloch-Walldorf, Bruchsal, Karlsruhe-Durlach, Rastatt, Baden-Baden and Offenburg. Since December 2003, line S3 of the Rhein-Neckar S-Bahn has operated on the Mannheim–Karlsruhe section of line and S4 (Speyer–Bruchsal) on the (Speyer–Karlsruhe) section.