[1][6][7] As constructed, the line was operated by steam locomotives, and used the Riggenbach rack system to overcome gradients of up to 12% on the approaches to each side of the Brünig Pass.

It also used the Riggenbach rack system on its final approaches to Engelberg, but with a very steep maximum gradient of 25%.

This involved constructing a bridge over the narrow Alpnachersee arm of Lake Lucerne, followed by the Lopper II tunnel, under a shoulder of Mount Pilatus.

In order to allow Engelberg trains to run over the Brünig line into Lucerne, the whole railway was converted to the same electrical system (15 kV  16.7 Hz AC), and new rolling stock acquired.

However, in June 2004, the Swiss Federal Council empowered the SBB to transfer the Brünig line to the LSE with effect from January 2005.

[1] At the end of 2009, the Zentralbahn took over the operation of the 1,435 mm (4 ft 8+1⁄2 in) (standard gauge) tracks of the Kriens-Luzern-Bahn between Lucerne and Horw.

The tunnel replaces a less direct surface alignment, allowing the abolition of several congested level crossings and the provision of double track.