Inauguration of Switzerland’s Hauenstein Base Tunnel Double-Tracking

The Hauenstein Base Tunnel, opened in the 1910s, has long served as one of Switzerland’s key North–South corridor passages. On December 21, 1937, Swiss Federal Railways completed the long-planned project to double‑track the tunnel. This upgrade was critical for accommodating surging traffic volumes between Basel and Olten, including both domestic passenger trains and international freight. The work required complex logistical planning, as the line remained partially operational throughout much of the construction process. Double‑tracking significantly reduced congestion and improved timetable reliability on the central Swiss network. The project reflected Switzerland’s broader interwar efforts to modernize and expand rail infrastructure, laying the foundation for today’s dense, high-efficiency national railway system.