In addition, four tunnel-wide single-track closures are planned. They will take place in 2024, 2026, 2027 and 2028, each during five weeks in the summer holiday period, when there is less traffic. During these closures, the SBB will renew the tunnel tracks.
The 8.1-kilometre-long, two-lane Hauenstein Base Tunnel was built between 1912 and 1916. The tunnel lies on the Basel–Olten railway line and crosses the Jura mountain range between Tecknau and Olten. In 2019, an average of around 100 goods trains and 320 passenger trains used the tunnel every day. The last comprehensive renovation work on the tunnel was carried out between 1980 and 1987.
Since then, SBB has regularly carried out selective maintenance and renewal work. As part of the general overhaul, SBB is now comprehensively repairing the tunnel vault. It is also renewing or replacing the tracks – i.e. rails, sleepers and ballast - and laying new cables. The track drainage is being improved. In addition, SBB is renewing and modernising the tunnel self-rescue devices,
Various technical installations are also being adapted, including the ventilation shaft in Zeglingen. In Tecknau and Trimbach, a new emergency basin is being built. These will enable more wastewater to be retained in the event of incidents in the tunnel than with the existing shaft solutions. The aim of the major renovation is to ensure safe, trouble-free rail operations in the tunnel for the next 25 years. The cost forecast for the project is currently around 146 million euros.