At a length of 3,360 metres (11,020 ft),[note 1] it was the second longest railway tunnel of Switzerland at the time of its opening.

[2] Originally the line was planned to only cross the Zimmerberg range and then follow the Sihl valley in the open to Walterswil near Baar, leading to Zug.

[2][4] Since both the Sihltal railway line and a proposed (but later failed) line coming from St. Gallen were planning to connect to Zug through the same tunnel, there were demands to build the Albis tunnel as double-track, which was opposed by the NOB and ultimately rejected by the Federal Council in favour of a certain and timely execution.

[6] Engineer Franz Vital Lusser had founded this company and amassed enough money for the security deposit required by the contract, which he had failed to procure when the NOB published the first invitation to tender in 1891.

[7] Overall, the construction of the Albis Tunnel finished one year earlier than planned,[9][14] despite it originally being estimated to be the most time-consuming part of the Thalwil-Zug line.