I also have this idea about making quadricycles, which would be a replacement vehicle for the modern car, with it's combustible engine. I mean why can't we make a pedal car (like we had when we were kids, remember??) out of lightweight metal that has 2 front seats and a supply bed for groceries and supplies, etc., and a set of pedals in front of each person, on the floor, so that either person could pedal the car. The pedals would have to have about 23 gears to get up to high speed or get up hills etc. but this would be a great adjustment, and do a lot to improve the world situation. They would have to have very lightweight metal frames, resembling a bicycle, but being a car. If it's cold out you might have to bundle up. If it's raining you throw on the top. People would be healthier and so would the whole planet. It's only a partial solution though because it wouldn't be too good on steep hills and would have some weight limitations too, but might work very well in flat areas or for localized gettin around. I don't know...hmm...
Now people will say, "O yeah, but people with jobs will have to build them". Fair enough. I'm not against people working together to build such things in a small localized community factory or something, as long as the job is not just about money, but serves a just purpose to the community and the world at once and doesn't require more than around 20 hours of job time per week or so. I'd think that'd be about the most a homesteader could reasonably spare...if that.