In the course of industrialisation, the lines were repeatedly rebuilt and realigned and the current lines emerged in the mid-20th century: The route that operated from 1886 to about 1938 started in Brunswick North station (Braunschweiger Nordbahnhof), the BLE’s centre of operations.

The line continued through Immendorf and Barum to the south and then turned to the west and the northwest.

However, even this mainly promoted regional development as the largest cities of the duchy had already been directly connected by the Brunswick–Bad Harzburg railway since 1838.

In order to develop the new industrial complex that is now Salzgitter AG, the BLE was nationalised by the Nazi Government in 1938.

After the war, a well-developed northeast half of the Brunswick–Drütte line contrasted with the less-developed rural western section, which passed south of the industrial sites and new residential areas.

In 1956, a line was built from Salzgitter-Bad to Salzgitter-Drütte, creating a more direct route for the Brunswick–Kreiensen railway.

Deutsche Bundesbahn discontinued passenger services on the section between Lebenstedt and Derneburg at the commencement of the summer 1984 timetable on 2 June.

The old railway embankment along with its track bed still exists east of the Bosch factory in Salzgitter, including several bridges over roads and the Fuhse.

The now abandoned proposal for a RegioStadtBahn Braunschweig (Brunswick Regional Stadtbahn) would have integrated the route to Lebenstedt.

The railcars would have left the current route before its terminus and run on a new tram line to a point closer to the centre of the district.