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.
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 would begin from Haag through Reichenau. Then it would be an expressway again until after Mesocco. The final kilometres linking it from Roveredo to the A2 motorway would be 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 San-Bernardino tunnel, between Thusis and Soazza, there is no central structure to separate the two carriageway directions; each lane is about 50% larger than on a main road, and overtaking (using part of the carriageway reserved for the other direction) is actually allowed where signposted. The expressway finds it way through the Alps by means of the San Bernardino tunnel, which is 6.6 km (4.1 mi) 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).
The A13 continues the A1 on the shores of 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: 120 km/h (75 mph) on all motorway parts; 100 km/h (65 mph) or at times 80 km/h (50 mph) on expressway parts. Speed checks do appear and penalties can be severe.
Tolls: Covered by CHF 40 annual motorway toll sticker.
The A13 starts in St. Margrethen, Canton of St. Gallen right after the A1. Afterwards, it crosses through the entire Rhine Valley, connects along the border with Austria and Liechtenstein, towards Sargans, where A3 joins the A13.
The highway then heads to Chur, the capital of Grisons, and turns southwards at Reichenau, where one can divert to drive along the Alps on the main road to Flims-Disentis-Andermatt-Brig (summer only), whereas A13 leads to Thusis (about 600.0 metres or 1,968.5 feet up).
From Thusis the A13 climbs an altitude difference of some 1000 metres to the 6.6 km (4.1 mi) long San Bernardino Tunnel at around 1,650 metres (5,410 ft).
After the tunnel the road is marked by many galleries and strong avalanche-control curves back down into the Misox, using two long bridges to allow wide turns in this steep valley. At Soazza, shortly after Mesocco, the street again becomes a highway. The A13 continues downhill and joins, shortly before the Ticino capital Bellinzona, merging with A2 at an altitude of 240 m (787 ft).
Between Ascona and a roundabout south of Gaggiole in the Canton of Ticino, A13 is extended as the N13 highway; however, it is indicated by the crossed-out highway signs that Switzerland motorway sticker on this route is not necessary. Locarno is bypassed with the 5-km (3-mi) long Mappo–Morettina Tunnel. In this tunnel, there is one lane for each direction.
Originally, a largely non-divided section of the expressway from Sargans to the north has long been regarded as a particularly dangerous stretch: time and again, it experienced severe front-end collisions. In the period from 1979 to 2002, 96 people died on the A13, five times more than usual in Switzerland's highways.
On 16 September 2006, a fire broke out in the Viamala Tunnel, after a head-on collision between a tour bus and a car, which killed nine people. Involved in the collision was a second passenger car. At least four other vehicles were affected.
As a major transit route, shifting traffic from the A13 is a major concern. For the future, the introduction of an Alpentransitbörse is being discussed.