The key to eliminating the use of petroleum is to change the way buildings are placed in relation to each other. In other words, instead of the sprawl of spread out suburbs, we need density of old main streets and city centers. While not everybody would want to live in a city as dense as New York City, and particularly Manhattan, residents of New York City contribute less than 30% of the greenhouse gases of the average American, according to David Owen in his book, "Green Metropolis". Therefore, if everybody lived in a New York City, U.S. greenhouse gas emissions would plummet by 70%. This is because the way we place buildings in relation to each other has a profound influence on the way we use energy.
There used to be something called a "town" in the United States, with a Main street where all the commercial activity took place, generally with a train station situated in a strategic position so that goods could easily be transported from the station. Almost all housing was within walking distance. Since we can now use slow electric cars, homes need not be within walking distance, but they should still be close to a town center. Since town centers have almost ceased to exist, part of a "densification" program will involve what is called "infilling", that is, placing new, large buildings in the middle of a newly constructed town center.
Even most city centers no longer have walkable residential neighborhoods. Instead, they survive as business districts and become deserted after working hours. A densification campaign therefore would be needed in most cities as well.
Let's assume, for the sake of simplicity, that 25% of the 100 million American households would gladly live in a 250-unit apartment building in a walkable neighborhood. Then if a government-financed program built 100,000 such units, at $50 million each (assuming $200 per square foot, for 1000 square foot apartments), spread among the downtowns of dozens of cities and towns, the cost over 20 years would come to about $250 billion per year. We would then have one quarter of the population in walkable neighborhoods. Perhaps another 25% would be in suburbs dominated by single family homes that would be close enough to the city and to town centers that they could live comfortably with small electric cars, and another 25% that would still need cars to a great extent, so perhaps we could have another 20 year program to get fully half the population in walkable neighborhoods. About 5% of the population now lives in walkable neighborhoods, so after 40 years we would have 20% of the population that might be involved mostly with agricultural or stewardship of natural ecosystems.
Assuming $50,000 per job, we are talking on the order of 5 million jobs for this program. This program alone would eliminate most unemployment.