The bus could operate well on roads with gentle curves, and the lane lines already painted on the road will adequately guide motorists.

Are there that many crashes inside tunnels?

The undercarriage of the bus could be made stout enough that the passenger compartment isn't crushed during most collisions although the roof of an overheight car passing underneath would be crushed very easily. Actually the undercarriage would have to be quite stout so the bus doesn't trapezoid-collapse itself to the side during normal operation.

I am led to believe that the annual income to price of car ratio in China for those owning cars is somewhat less than in the U.S. making a damaged car a more significant hardship in China. In turn this should lead to more careful driving.