In order to expand freight traffic and transport goods faster through Switzerland, Swiss Federal Railways has been commissioned by the federal government to build a 4-metre corridor (clearance height for transporting semi-trailers on trains) by 2020. The largest single project is the construction of the new Bözberg tunnel between Effingen and Schinznachdorf in the canton of Aargau. The dimensions of the current tunnel are not suitable for 4-metre trains.
 
Work on the new Bözberg tunnel began in 2015 in several stages and was completed by 2020. The old tunnel has since been decommissioned and converted into a service and rescue tunnel.
 
The project cost CHF 350 million.