In
2015 (I accidentally used 2015 numbers and am too lazy to go back and fix that), Chicago's total bus ridership was approximately 275 million rides. When I first moved to Chicago, bus ridership was approximately double rail ridership, but in 2015 rail ridership was about 242 million, so through a combination of declining bus ridership and increasing rail ridership they're fast approaching parity. Some of these lines exceed some of Chicago's 'L' line ridership. In 2015, the Yellow Line would have had about 884,000 riders if it'd been a normal year (they had a outage caused by a construction project adjacent to the tracks), the Pink Line had about 5.6 million, the Purple Line in Evanston about 3.3 million, and the Orange Line had about 9.1 million.
In 2015, Chicago's highest ridership bus lines were as follows:
Route, annual ridership, description of service area:
9/Ashland, 8.9 million, north-south route serving the near-west areas from Edgewater to Uptown/Ravenswood/Lincoln Square to Lakeview to Wicker Park/Bucktown to the West Loop to Bridgeport and the South Side
79/79th Street, 8.7 million, east-west route serving the far south side from the lakefront South Shore neighborhood west to the Beverly neighborhood
49/Western, 7.5 million, north-south route serving Western Avenue, one of the major north-south corridors in the middle-west portions of the city from Beverly in the south to McKinley Park on the SW side, Logan Square and Lincoln Square on the NW side and West Ridge on the north. If the 49B/North Western and X49 express buses that extend the corridor, the total for the corridor would be about 9.2 million riders for the corridor.
66/Chicago Ave, 7.4 million, east-west route from the lakefront Gold Coast neighborhood to the Ukrainian Village, Humboldt Park, and Austin neighborhoods
77/Belmont, 7.0 million, east-west route serving the mid-north area from the lakefront Lakeview neighborhood to the Belmont-Craigin area which is highly Polish immigrants
8/Halsted, 6.8 million, north-south route from Wrigleyville/Lakeview through Lincoln Park, River West, West Loop/Greektown, past UIC/University Village, Bridgeport, Englewood and the far South Side and the southern city limits. If the 8A/South Halsted route were included, the corridor would total about 7.9 million.
4/Cottage Grove, 6.7 million, a north-side line from East Loop/Lakeshore East south along Michigan Avenue south past McCormick Place convention center, through Bronzeville, Kenwood, Hyde Park/U of C, and Pullman Historic District and Lake Calumet
53/Pulaski, 6.3 million, a north-south route starting near the north city limits and running south along Pulaski through Belmont-Cragin, western Logan Square and Humboldt Park, through Garfield Park and North and South Lawndale, ending in the Little VIllage, where it connects to the 53-A/South Pulaski route that serves the south side with 2.4 million riders. Taken together the corridor has 8.7 million riders, annually, which would make it the second or third more traveled corridor in the city.
3/Martin Luther King, Jr. Drive, 6.1 million, a north-south from Watertower Place south along Michigan Avenue through the South Loop, past the McCormick Place convention center, through Bronzeville and past IIT, through Washington Park, through Chatham and ending at the 95th Street Red Line terminal
22/Clark, 6.1 million, a major north-south North Side route running from the Howard north terminal for the Red Line south along Clark through Rogers Park, Edgewater/Andersonville, Uptown, Lakeview, Lincoln Park, the Gold Coast, River North, the Loop and then terminating in the South Loop. The 36/Broadway route overlaps 22/Clark for a substantial stretch. Taken together that would be 10.8 million riders. If including the 24/Wentworth route, which essentially continues the Clark route south from the South Loop, that total increases to 11.5 million for the entire corridor.