King's 401, commonly referred to as 401 and also known by its official name as the Macdonald–Cartier Freeway or colloquially referred to as the four-oh-one,[3] is a controlled-access 400-series in the Canadian province of Ontario. It stretches 828 kilometres (514 mi) from Windsor in the west to the Ontario–Quebec border in the east. The part of 401 that passes through Toronto is North America's busiest ,[4][5] and one of the widest.[6][7] Together with Queb