Switzerland and seven other alpine nations signed the Alpine Convention on Tuesday, including a measure designed to limit the environmental damage caused by traffic.
Along with ministers from seven other alpine countries, Switzerland approved the traffic protocol on the second and final day of the Alpine Conference in Lucerne.
The transport agreement means no new transalpine roads can be built. Austria had expressed reservations about the accord.
The agreement also obliges signatories to keep traffic below levels where it would threaten the well-being of humans, flora and fauna.
The signing of the transport protocol was not a problem for Switzerland, which already has stricter laws on major road development in the mountains than those enshrined in the protocol itself.
Two other accords - covering energy and the settlement of disputes - were also signed by the Swiss.
Switzerland had previously signed five of the eight convention protocols, covering tourism, the protection of nature, alpine economy, alpine forestry and land management.
The protocols have met resistance both in parliament, which has yet to ratify them, and in certain mountain cantons opposed to some of the provisions.
There is, however, growing pressure, to see the convention applied as soon as possible. The International Commission for the Protection of the Alps (CIPRA) has asked for a heavy-truck tax to be introduced all over Europe.
The organisation, which includes the Swiss Transport and Environment Association and the Alps Initiative, also wants road traffic to be reduced and opposes the building of a second tunnel be built under the Gotthard pass.
The Alpine Convention brings together Switzerland, Germany, Austria, France, Italy, Liechtenstein, Monaco and Slovenia.
swissinfo with agencies