In my part of America, Iowa specifically, public transportation is pretty much nonexistent. Population density is simply too low to support it. Recently I've restricted my driving on freeways to 55 mph, regardless of speed limit and adjusted my shifting habits to shift as low as I can without bogging the engine. In my car I've started shifting at 1500 rpm, and on my bike I've been shifting at 3000 rpm. This has netted me about a 3.5 mpg gain in my car, but hasn't really had an impact on my motorcycle's mpg at only about .6 mpg gain. Not huge improvements by themselves, but if enough people modified their driving to gain maybe 3 mpg, I believe it could have a significant impact.
I think a big problem, especially here in America, is the idea that you need a huge 4x4 truck or SUV for everyday transportation. For some reason, people have forgotten that just 25 years ago, hardly anyone owned a four wheel drive truck or SUV. Everyone drove cars, and everybody got around just fine. Do I need an 8 foot truck bed to carry my groceries home from the store? No. Do I need four wheel drive? No, I buy snow tires for the winter time and my car gets around fine. ( Remember snow tires?) It seems like most Americans have completely forgotten that four wheel drive is not necessary in the winter time with right tires. Big truck and SUV manufacturers spend a lot of money marketing the idea to us that we need big 4x4 trucks and SUVs to make driving through 4" of snow safe. And that we need the 100 cubic feet of cargo space that their SUV offers. But how often do I really need to haul 100 cubic feet of something? Not very often. If I need to haul a lot of something, or if I'm moving all my belongings to a new residence, I can rent a U-Haul truck for what seems like nothing compared to the cost of purchasing a truck or SUV.