I pretty much hate mass transit, but understand that there is a place for it.
I mostly don't like waiting for things, or sitting next to strangers, or stopping every 20 seconds.
But I was looking at a chart last night that showed the comparative fuel efficiency of a variety of transport options and it is undeniable that buses are quite efficient when they are full.
They are also the least efficient transport option in existence when they are empty.
My idea: only run buses during times of the day when they are the most efficient option, then subsidize other transport options (like taxis) during the quiet hours. I don't know what the exact rate structure should be, but the city would save a silly amount of money by only running buses 10-14 hours/day instead of 24.
The reduction of diesel particulate emissions would be even greater than the reduction of energy consumption, since most buses are diesel powered.