The A-21, also known as the Pyrenees Motorway, was designed as a high-capacity highway cross-connecting Navarre and Aragon. The construction design defines an entirely new motorway section 5.393 km in length, between K.P. 317.00 and 323.00, with a design speed of 100 km/h. Key structures include 5 viaducts of up to 280 m in length, 11 cross-drainage culverts, underpasses, an overpass over the Camino de Santiago and a “semi-cloverleaf dumbbell” interchange.