King's Highway 427 (pronounced "four twenty-seven"), also known as
Highway 427 and colloquially as
the 427, is a
400-series highway in the
Canadian province of
Ontario that connects the
Queen Elizabeth Way (QEW) and
Gardiner Expressway with York Regional Road 7 (formerly
Highway 7) via Highway 401. An arterial extension, known as York Regional Road 99, continues north to Zenway Boulevard. It is Ontario's second busiest freeway by volume and third busiest in
North America, behind Highway 401 and
Interstate 405 in
California. Like Highway 401, a portion of the route is divided into a
collector-express system with twelve to fourteen continuous lanes. Notable about Highway 427 are its several multi-level interchanges; the junctions with QEW and Highway 401 are two of the largest interchanges in Ontario and were constructed between 1967 and 1971, while the interchanges with
Highway 409 and
Highway 407 are more recent and were completed in 1992 and 1995, respectively.