A second track was laid between Stuttgart and Renningen in 1932–1939.
Electrification on the section from Stuttgart-Zuffenhausen to Leonberg was completed on 15 May 1939 and on the section from Leonberg to Weil der Stadt on 18 December 1939.
Class E 44 electric multiple units were used on the electrified section; after the Second World War, class E 52 sets were used.

Since 1978, the Stuttgart–Weil der Stadt section has been integrated as line S 6 of the network of the Stuttgart S-Bahn.
At first DMUs continued to Calw as feeders to the S-Bahn.
As part of the establishment of the S-Bahn, a 1 kilometre-long flying junction was built in Zuffenhausen station for the line to Weil der Stadt with an elevated platform and ramps with a 3.0 percent grade.

On 3 December 1988, Stuttgart-Weilimdorf station was opened at a cost of just under DM five million.
In October 2003, a second track was put in operation between Renningen and Malmsheim.
This allows S-Bahn services to operate with longer travel times, but greater stability, with train now scheduled to cross in Malmsheim rather than in Weil der Stadt.
The longer travel time results from the need for trains to stop in Renningen to meet S-Bahn trains on line S 60, which commenced in December 2012.
A second track was laid between Stuttgart and Renningen in 1932–1939. Electrification on the section from Stuttgart-Zuffenhausen to Leonberg was completed on 15 May 1939 and on the section from Leonberg to Weil der Stadt on 18 December 1939. Class E 44 electric multiple units were used on the electrified section; after the Second World War, class E 52 sets were used.
Since 1978, the Stuttgart–Weil der Stadt section has been integrated as line S 6 of the network of the Stuttgart S-Bahn. At first DMUs continued to Calw as feeders to the S-Bahn. As part of the establishment of the S-Bahn, a 1 kilometre-long flying junction was built in Zuffenhausen station for the line to Weil der Stadt with an elevated platform and ramps with a 3.0 percent grade.
On 3 December 1988, Stuttgart-Weilimdorf station was opened at a cost of just under DM five million. In October 2003, a second track was put in operation between Renningen and Malmsheim. This allows S-Bahn services to operate with longer travel times, but greater stability, with train now scheduled to cross in Malmsheim rather than in Weil der Stadt. The longer travel time results from the need for trains to stop in Renningen to meet S-Bahn trains on line S 60, which commenced in December 2012.
Black Forest Railway (Württemberg)