Advertisement 1 Author of the article: • The World is a Stage • • Article content The Macdonald-Cartier Freeway, aka Hwy 401, is the longest 400-series highway in Ontario, North America’s busiest freeway, and one of the widest and busiest highways in the world. Advertisement 2 Article content We apologize, but this video has failed to load. Try refreshing your browser, or tap here to see other videos from our team. Half a million people a day use the section that runs across Toronto.