A new tunnel is being opened in canton Aargau to ease congestion at one of Switzerland's worst traffic black spots.
The third Baregg tunnel will be accessible to drivers from mid-June, but tailbacks are not expected to improve before 2004.
The Baregg is on the busiest stretch of motorway in Switzerland, which runs between Bern and Zurich. Traffic jams are an everyday fact of life.
When the first tunnels were opened in 1970, only 15,000 vehicles a day used them. Today the number is closer to 100,000 - 80 per cent of which is commuter traffic.
Planning for the new tunnel began in 1991, and it took three years to build. The total cost for the entire project should run to at least SFr350 million.
The two older tunnels still have to undergo renovation before the project is completed, but vehicles should have access to six lanes by the summer of next year.
Speaking at the opening of the new 1.1-kilometre tunnel, Transport Minister Moritz Leuenberger warned that adding extra lanes to the country's motorways would not solve Switzerland's traffic problems.
However, in a speech to the 500 guests present at the opening, Leuenberger promised that Switzerland's motorway network would be completed despite a SFr3.5 billion ($2.68 billion) federal savings plan.
But he admitted that its completion could be delayed in less populated areas such as cantons Jura and Valais, which have already been waiting years for improvements.
Leuenberger called on the cantons to establish common transport policies to ease congestion.
swissinfo with agencies
Tunnel length: 1.1 kilometres.
Cost of the Baregg project: nearly SFr350 million.
Up to 100,000 vehicles pass through the Baregg zone on the A1 motorway between Bern and Zurich every day.
Once the project is completed in 2004, six lanes will be available to drivers.