<Table> <Tr> <Td> ← Highway 400 </Td> <Td> </Td> <Td> Highway 402 → </Td> </Tr> </Table> <Tr> <Td> ← Highway 400 </Td> <Td> </Td> <Td> Highway 402 → </Td> </Tr> <P> King's Highway 401, commonly referred to as Highway 401 and also known by its official name as the Macdonald--Cartier Freeway or colloquially as the four - oh - one, is a controlled - access 400 - series highway in the Canadian province of Ontario . It stretches 828.0 kilometres (514.5 mi) from Windsor in the west to the Ontario--Quebec border in the east . The part of Highway 401 that passes through Toronto is North America's busiest highway, and one of the widest . Together with Quebec Autoroute 20, it forms the road transportation backbone of the Quebec City--Windsor Corridor, along which over half of Canada's population resides and is also a Core Route in the National Highway System of Canada . The route is maintained by the Ministry of Transportation of Ontario (MTO) and patrolled by the Ontario Provincial Police . The speed limit is 100 km / h (62 mph) throughout its length, unless posted otherwise . </P> <P> By the end of 1952, three individual highways were numbered "Highway 401": the partially completed Toronto Bypass between Weston Road and Highway 11 (Yonge Street); Highway 2A between West Hill and Newcastle; and the Scenic Highway between Gananoque and Brockville, now known as the Thousand Islands Parkway . These three sections of highway were 11.8, 54.7 and 41.2 km, (7.3, 34.0 and 25.6 mi), respectively . In 1964, the route became fully navigable from Windsor to the Ontario--Quebec border . In 1965 it was given a second designation, the Macdonald--Cartier Freeway, in honour of two Fathers of Confederation . At the end of 1968, the Gananoque--Brockville section was bypassed and the final intersection grade - separated near Kingston, making Highway 401 a freeway for its entire 817.9 - km length . On August 24, 2007, the portion of the highway between Glen Miller Road in Trenton and the Don Valley Parkway / Highway 404 Junction in Toronto was designated the Highway of Heroes, as the road is travelled by funeral convoys for fallen Canadian Forces personnel from CFB Trenton to the coroner's office in Toronto . On September 27, 2013, the Highway of Heroes designation was extended west to Keele Street in Toronto, to coincide with the move of the coroner's office to the new Forensic Services and Coroner's Complex at the Humber River Hospital . </P>

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