A-1 (autovía) replaces Carretera Nacional N-I
The A-1 (also informally known as Autovía del Norte; Basque: Iparraldeko Autobia) is a Spanish autovía route which starts in Madrid and ends in Irun. It replaced the former national road from Madrid to France, the N-I. It carries the designation of European route E05, and, as one of the major north-south arteries of Spain, is one of the country's busiest highways.
Between Burgos and Armiñón there is a toll alternative for this autovía, the autopista AP-1.
In 2011, work was ongoing to bring the section between Burgos and Madrid up to modern standards.