 It is one of the most-used roads in Castile and León, as it is frequently used by drivers travelling between France and Portugal.Conversion of the N-620 to autovía standard began in the mid-1980s, when the section between Palencia and Valladolid was upgraded to dual carriageway with same-level junctions.During the 1990s, the Burgos - Palencia and Valladolid - Salamanca sections were upgraded in a similar manner, but with grade-separated junctions and slip roads; the junctions on the Palencia - Valladolid section were improved accordingly at a similar time.