In the 1940s and 1950s, the construction of the General Paz Avenue beltway that surrounds the city along its border with Buenos Aires Province, and the freeways leading to the new international airport and to the northern suburbs, heralded a new era for Buenos Aires traffic. Encouraged by pro-automaker policies that were pursued towards the end of the Perón (1955) and Frondizi administrations (1958–62) in particular, auto sales nationally grew from an average of 30,000 during the 1920–57 era to around 250,000 in the 1970s and over 600,000 in 2008. Today, over 1.8 million vehicles (nearly one-fifth of Argentina's total) are registered in Buenos Aires.