[NoTargeT]

Busses can also use biofuel, hydrogen or electricity, all of which have already been implemented at places. Next to that, even if they would use gas, they use a lot less then when all 30 people in it would travel by car themself. Plus in built up areas USA residents have a large tendency to commute alone in their car. (90+% is not uncommon in cities).
I agree though that a lot more is needed. Decentralising of bussinesses and production is one. It's simply not costeffective anymore to centralise bussinesses and have personal and good being transported to and from it. Decentralising energy production is good too. Here in the Netherlands the first cities are impementing rules about new houses only being allowed to be built if they can supply their own energy (by solar, wind or earthwarmth power). Producing electricity, hydrogen etc by replenishable energy (solar, wind, water, tide, wave) etc. is a must as well. Dutch scientists are also making good progress of developing winning electicity at places where fresh and salt water mix (e.g. where rivers meet oceans). Also recycling is important, recycling often takes a lot less energy then producing from raw materials, and offcourse energy isn't the only thing we might run out of. IMHO a complete redesign of economy and society is our only ticket out of this mess. Just being more fuel efficient alone will only slow down things, but won't help in the end, except buy us a bit more time.
When it comes to areas with a low population density the areas will need to be redesigned so people live close to their work. With gasprices rising it will pass the point where living 12 miles from work simply isn't cost efficient anymore, because fuel to get to work will start costing you half of what you'll earn. Simple as that.