A quick Google, and you might think it’s Vancouver’s 99 B-Line:
It depends, then, on what you consider “North America.” Technically, it includes all 23 independent states as far south as Colombia – which means, of course, that Mexico is part of North America.
In which case …
In July 2005, the Metrobus corridor (in Mexico City) began operation on Insurgentes Avenue. It was the first BRT corridor in the city, extending over 20 kilometers (12.4 miles), with central stations. The number of passengers has rapidly increased since then from 250,000 daily in 2005 to 270,000 in 2007, an annual increase of approximately 10%.
In 2008, the corridor was extended nine kilometers (about 5.5 miles) to the south, and by the end of the year, the Line 2 in the Eje 4 Sur began operating twenty kilometers (12.4 miles) from east to west.
In 2009 the demand of the system grew to 480,000 daily passengers. In 2011 with the construction of the Line 3 in the Eje 1 Poniente, Metrobus increased 17 kilometers (10.5 miles), consolidating 67 km (41.6 miles), and 710,000 trips per day.
Maybe Darren Davis of Auckland Transport (who alerted us to these facts) can tell us what the daily volume of the Insurgentes line by itself is today – but one thing for sure: if the B-Line is going to be the busiest bus route in North America, it will need a few hundred thousand more passengers per day. Even if it feels like it already has.