King’s Highway 401, also known by its official name as the Macdonald–Cartier Freeway and colloquially as the four-oh-one, is a 400-series highway in the Canadian province of Ontario stretching 817.9 kilometres (508.2 mi) from Windsor to the Quebec border.
The segment of Highway 401 passing through Toronto is the busiest highway in North America, and one of the widest and busiest in the world.Together with Quebec Autoroute 20, it forms the transportation backbone of the Quebec City – Windsor Corridor, along which over half of Canada’s population resides. The entire route is maintained by the Ministry of Transportation of Ontario (MTO) and patrolled by the Ontario Provincial Police. The posted speed limit is 100 km/h (62 mph) throughout its length. (via wikipedia)