Highway 401-- also known as the MacDonald-Cartier freeway is a stretch of highway in Canada that connects Windsor, Ontario and ends at the Ontario-Quebec border where it becomes Quebec Autoroute 20 before continuing on to Montreal.

The section of highway 401 that passes through Toronto is among the widest and busiest freeways in the world, peaking at 500,000 cars per day (in comparison to Los Angeles' Santa Monica Freeway at 480,000) and expanding to 18 lanes in some sections.

Due to heavy Canada-USA trading, it is also the busiest truck route on the planet.

Highway 401 also crosses the Don River Valley at Hogg's Hollow Bridge, which is the busiest multi-span bridge in North America-surpassing even the Brooklyn Bridge.
Driving on highway 401 at noon is a death sentence.
by AssBlaster55 February 24, 2012
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A very long stretch of parking lot in southern Ontario. Occasionally used as a highway.
"Man, I hate driving on the Highway 401 every morning."
by Paperpaper22 June 27, 2016
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