Southwest of Bordeaux, the A63 is a major focus of the regional motorway network. Forming a large artery almost straight through the vast expanses of flat Landes de Gascogne, it crosses the south of Gironde and Landes (passes near Dax but avoids the prefecture, Mont-de-Marsan) before joining Bayonne and the Basque Country, to Irun, on the Spanish border, the main border crossing. Particularly popular, especially during the summer, it supports an average daily traffic of 34,000 vehicles (8,000 trucks), increasing to 50,000 vehicles (10,000 trucks) during the months of summer. The other border crossings, less frequented but less direct, are the Somport tunnel and Col du Pourtalet.