I've oft wondered why they don't use LPG for busses? Virtually no
pollution other than CO2. Engines are much quieter too.

abroad it's fairly common to see CNG powered busses, the gas tanks being on
the roof under a fiberglass hump,

wouldent trolley busses be even better? mind even the ones in zurich have a
small diesel engine on board, used for when they unhook from the power wires
to go into the depot/garage, the river starts a small diesel engine which
allows the bus to do about 5mph, not sure if it's a generator or directly
driving the bus,