There was increasing support for a more direct rail connection between Burgdorf and Thun to shorten the route by almost 13 kilometres, which is 53 km via Bern.

The line used the track of the Emmen Valley Railway from Burgdorf to Hasle-Rüegsau, including the intermediate stations of Steinhof and Oberburg.

The positive experience with three-phase operations on the Luzern–Stans–Engelberg railway (Stansstad-Engelberg-Bahn) and especially the influence of the electrical engineer Emil Blattner, who was both professor of electrical engineering at the Burgdorf College of Technology (now part of the Bern University of Applied Sciences) and a councillor of Burgdorf, led to a bold decision by the Burgdorf-Thun Railway to electrify the line at 750 volts and 40 hertz three-phase from the start of operations on its relatively long line.

[2] Permission to use a high voltage was granted by the Railway Department without regard to the safety of passengers and staff.

The electric operations enabled a tight timetable for the time, which was useful in view of the many connections in Burgdorf, Konolfingen and Thun.

The transformer power of 450 kVA was designed for the load of a so-called double train of 100 tons weight.

The BTB was not affected by the crisis of the First World War and, on the contrary, revenue from both passenger and freight traffic tripled from 1914 to 1920.

In the 1930s, the line was switched in stages from three-phase to single-phase 15 kV  16.7 Hz AC: For operation with single-phase AC, the BTB, the EB and the Solothurn-Münster-Bahn (Solothurn-Moutier Railway, SMB) jointly procured eight Be 4/4 locomotives and twelve CFe 2/4 railcars.

On 4 September 1949, the derailment of a train coming from Thun at the entrance to Heimberg left two dead and six injured.

Additional services run in the peak hours in the morning and in the evening between Konolfingen and Burgdorf.

It runs on an almost constant grade along the Biglenbach through Schafhausen, Bigenthal, Walkringen to Biglen to the highest point on the line at 770 metres above sea level.