Shanghai blogger Wang Jianshuo points out a less-than-expected reason why riding the bus is faster than driving on his commute: ad hoc protest against traffic enforcement:
Bus drivers don't follow the traffic rule as strictly as other car drivers. They just drive wildly, and policemen tend not to care about them. Why? I saw some cases when the policeman stops the bus, and the whole bunch of people on the bus surrounded the policeman and protest to ask the policeman release the driver.
This comes in addition to a more engineered factor, the bus-only lane on highways. People bending rules both help and hurt bus travel speeds in Wang's post. Above, they prevent bus drivers from being punished for illegal expediency. But meanwhile, as Wang notes, lots of private cars violate the bus only lane. The bright side is that the bus lane still remains fast enough to increase efficiency.