Due to the different companies that manage the different parts of the motorway, it is often referred to as formed by five sections:
Turin-
Milan,
Milan-
Brescia,
Brescia-
Padua,
Padua-
Venice and
Venice-
Trieste. As it runs through the whole
Pianura Padana, which is a densely populated and highly industrialized area, the A4 is one of the busiest motorways in Italy. Before World War II, three sections of the motorway were built: Turin-Milan, Milan-Brescia and Padua-Venice. The first section built was Milan-Bergamo, which opened on 24 September 1927, being just the second motorway to open, following the Autostrada dei Laghi in 1924/25. On 29 August 1931, it was extended to Brescia. On 25 October 1932, the Turin-Milan section opened, and on 15 October 1933, the Padua-Venice section. The two sections became connected on 10 February 1962, when the Brescia-Padua section opened. The Venice-Trieste section was opened on 22 February 1970. The original road through Mestre, now designated A57 and named "Tangenziale di Mestre", opened on 3 September 1972. A4 is a dual-carriageway, six-lane motorway for most of its length. The stretch between Milano Est
tollgate and
Bergamo has been an eight-lane motorway since 30 September 2007. The stretch from
Venice to
Trieste is instead still a four-lane motorway, but it is planned to upgrade this stretch over motorway to six lanes. ==Operators==