Which is the Busiest Highway in North America?

June 15, 2023

When it comes to road-building, Texas has a lot of clout. The state’s highways are a trove of big-buck ideas, from sprawling multilane freeways to the widest in the world. But which is the busiest?

To determine how busy a highway is, transportation agencies typically use an estimate known as Average Annual Traffic, or AADT. This number is based on how many vehicles pass over a stretch of roadway, averaged over 365 days. CityNews used AADT data from various sources, although we were careful to only use data collected before the COVID-19 pandemic hit.

The answer, at least in terms of Canadian highways, is clear-cut: Highway 401 as it passes through Toronto is the busiest highway in North America. A few years back, this section of the highway earned the nickname ‘Killer Highway’ because of how often it was the site of deadly accidents. Despite its infamous reputation, however, the road is actually quite safe.

While the 401 is the most crowded highway in Canada, it’s not the world’s busiest. That honor belongs to the Katy Freeway in Houston, which has 26 total lanes (eight through and four feeder).

Still, there’s no denying that these highways are packed, and they deserve a place on this list of the Most Inconvenient Highways. So, if you’re planning on taking to the road this summer, keep this article handy. And remember: When in doubt, Always Rule the Road with These Smart Driving Strategies.


Traffic Dave is on a mission to help traffic engineers, transportation planners, and other transportation professionals improve our world.
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