The A13 is a motorway, at times an Autostrasse (expressway), which runs from St. Margrethen in northeastern Switzerland through to Ascona in southern Switzerland, crossing the main chain of the Alps in the Grisons area. It is the southern half of European route E43. Construction The A13 started life as a road which was mainly an expressway, from the foggy beginnings at St. Margrethen through to Haag, opposite Liechtenstein. The motorway began at Haag and went through Reichenau. Then it was an expressway again until after Mesocco. The final kilometres linking it from Roveredo to the A2 motorway were an expressway. Today, the section from St. Margrethen through Haag has been thoroughly converted to a motorway. Due to the tough terrain, the transformation of the Graubünden section into a full motorway would be difficult. The route is challenging south of Chur, capital of the Grisons. The year-round opening of the route only became possible in 1967, when the San-Bernardino tunnel was built, including the approaching branches of the A13. Therefore, it sometimes appears to be more of a widened mountain road, rather than a motorway or an expressway. For the whole of the ramps towards the culmination at the San-Bernardino tunnel, between Thusis and Soazza, there is no central structure to separate the two carriageway directions; each lane is about 50 percent larger than on a main highway, and overtaking (using part of the carriageway reserved for the other direction) is allowed where signposted. The expressway finds its way through the Alps by means of the San Bernardino tunnel, which is in length. It also passes the Viamala gorge, where nocturnal shows tell the story of 2000 years of road construction through this obstacle (summer only). General information The A13 continues the A1 on the shores of the Bodensee, links with the A3 motorway at the Sargans junction at its northern branch, as well as the A2 motorway at Bellinzona, south of the Alps. It connects also with main roads heading for Flims-Disentis along the Alps or Klosters, St. Moritz via Julier Pass, and Italy (via the Splügen Pass). Main route: St. Margrethen - Buchs SG - Sargans - Landquart - Chur - Thusis - Splügen - Cassanawald tunnel - Hinterrhein - San Bernardino road tunnel - Pian San Giacomo - Roveredo - Bellinzona - Locarno - Ascona Speed limit: on all motorway parts; or at times on expressway parts.