Post-war period

Following the end of the Second World War in 1945, the Saar line was again divided in 1947. The section south of Saarhölzbach was now under the French controlled Railways of the Saarland (Eisenbahnen des Saarlandes, EdS), the northern section was first part of the Union of Southwest German Railways (Betriebsvereinigung der Südwestdeutschen Eisenbahnen, SWDE), which became part of Deutsche Bundesbahn (German Federal Railway) in 1951. With the inclusion of the Saarland in West Germany in 1957, the whole line became part of Deutsche Bundesbahn. But the stop for customs at Saarhölzbach was only abolished in 1959.

Electrification

Despite the strong mineral traffic, the Saar line was not one of the first lines of Deutsche Bundesbahn to be electrified. Electrification was first extended to Merzig and later to Saarhölzbach. Only in 1974 was the electrification completed to Trier and Koblenz. It is electrified at the standard German system of 15 kV, 16.7 Hz. It was proposed in the 1950s to electrify the lines of the Saar with the modern French electrification system of 25 kV, 50 Hz. Instead it was decided to canalise the Moselle between France and Germany.

Long distance services

In addition to regional passenger services, the line used to have long-distance express ("D-train", D-Zug, short for Durchgangszug, literally “corridor train”) services. The D-trains ran from Saarbrücken and Trier over the Eifel Railway via Gerolstein or over the Moselle line via Koblenz to Cologne. Until the electrification of the Trier–Koblenz line, D-trains ran fairly equally on both routes. Only afterwards was there a clear preference for the Moselle route.

In 1973 three pairs of City-D-trains ran via Koblenz and Cologne to Düsseldorf. These trains were replaced in 1978 by InterCity-Comfort services, which were similar but had no dining car.

The Saar line was included in the InterRegio network, development of which began in 1988. From 1991, there were D-train services at two-hour intervals connecting Saarbrücken, Koblenz, Cologne, Münster, Bremen and Cuxhaven, with a section of these trains running to Greifswald. This was complemented by express trains between Koblenz and Saarbrücken at hourly intervals. It was not until 1994, with the completion of the conversion of old rolling stock into the new InterRegio trains, that the D-trains were replaced by InterRegio services. In December 2002, the InterRegio services were all cancelled and the Saarland no longer has any long-distance connections.

Regional services

Regional services has always played a large role on the Saar line, with trains between Saarbrücken and Saarhölzbach being denser than on the northern section towards Trier. Already in 1989 City-Bahn Saar services operated on the line. This was an hourly service from Saarhölzbach (some starting in Trier) via Merzig, Saarlouis, Völklingen and Saarbrücken to Homburg. These services were reinforced every two-hour by express trains running from Merzig via Saarbrücken to Kaiserslautern, which only stopped on the Saar line in Dillingen, Saarlouis, Völklingen, although some also stopped in Beckingen and Bous. In 1995, the City-Bahn were rebranded as Stadt-Express services, which in 1998 was replaced by Regionalbahn (RB) and Regional-Express (RE) services.

In 1996 it was planned to replace the electrically hauled RE trains from Saarbrücken to Koblenz with diesel tilting trains from Saarbrücken via Trier to Cologne on the Eifel Railway. This project failed because of technical problems, so that RE services continue to run between Saarbrücken and Koblenz (Mosel-Saar-Express) with double-deck carriages. These connect in Trier with trains to Cologne. The Mosel-Saar-Express services runs every two hours and together with the RE 11 (Trier–Saarbrücken–Homburg (–Kaiserslautern)) services provide an hourly service on the Saar line.

In addition, RB line 71 services run from Trier via Merzig, Dillingen, Saarlouis, Saarbrücken, St. Ingbert, to Homburg. These services run hourly with S-Bahn-like railcars of class 425 and 426. Extra RB 71 services run between Dillingen and St. Ingbert to provide a 30-minute interval service.