They dart in and out of traffic nimbly, like a taxi. They accelerate and decelerate like a carnival ride, and like a taxi. They straddle all of the lane lines, like a taxi. There seem to be as many of them on the road as there are taxis. They stop every couple of blocks on their routes, but in between every stop, the enormous buses manage to dart across three to four lanes of traffic from the extreme left to the extreme right of whatever avenue they are driving.
The bus system is chaotic and decentralized, and the buses themselves spew a noxious mix of black exhaust; however, I must applaud the lack of a hub and spoke system. The decentralized nature of the buses means that you can catch a bus from somewhere near your home and go to within a few blocks of pretty much anywhere in the city.
Photo by Flickr user monkey.cl used under a Creative Commons license.