The N-135 road links Pamplona to France via Luzaide/Valcarlos and is 62 km in length. The project considers alterations to two sections of the N-135, maintaining a design speed of 100 km/h. The work was carried out in two phases; preliminary design and detailed design. The first of the sections, between Zubiri and Erro, is 6.8 km in length and crosses the Erro pass through a 2.3 km tunnel, a 150 m viaduct and 4 intersections. The second section, 2.5 km in length, alters the existing route in the final part of the Mezkiritz pass with a second tunnel 0.5 km in length and 3 intersections.