NO BIOFUEL CARS! NO CARS AT ALL! WHETHER YOU BURN PETROLEUM OR VEGETABLE OIL YOU STILL PRODUCE HEAT AND GREENHOUSE GASSES THAT PROMOTE GLOBAL WARMING! STOP KILLING THE PLANET! THE ONLY GREEN CAR IS ONE THAT IS PARKED AND TURNED OFF FOREVER!!!

I don't think it is necessary to completely give up anything that resembles the family car. If the crops grown really do produce a net amount of fuel for cars and busses, then I don't see any harm done. In that case, running the cars and busses on biofuels would not contribute to global warming.
There are estimates however that suggest that the crop harvesting does not always result in a net fuel production. That is, in some cases fossil fuel is actually consumed, at a net loss, to produce the biofuel. Consuming french fry oil and the like would seem to avoid this predicament somewhat. Does anyone have any figures to present on that one way or the other?

Long term, what needs to be done is to use solar power to run Personal Rapid Transit (PRT). PRT would transport people in 3 person cars to within 1/4 mile of their desination on a network of tracks that would have no stops at intersections.
Slowdowns due to congestion would be much less than with the conventional automobile because the cars could be run by computers at high speeds even in congested areas. Limitations would occur mainly when the stations where people get on and off the system were overloaded with cars. In that case, the cars that
could not unload would continue on around the 1/4 mile loop until they had an opportunity to unload.
This would represent a delay of about 2 minutes at a car speed of 30 mph.

I did some searching to find out the energy efficiencies involved in producing biofuels. As I suspected, I found some good news and some bad news:

From mauigreenenergy.org/biodieselfaqs.htm

"Biodiesel also has a positive energy balance, generating three or more units of energy for every unit required to make it. And because it is biodegradable and nontoxic, biodiesel poses little to no environmental threat while in transit.

Can biodiesel help mitigate global warming?

A 1998 biodiesel lifecycle study, jointly sponsored by the U.S. Department of Energy and the U.S. Department of Agriculture, concluded biodiesel reduces net CO2 emission by 78 percent compared to petroleum diesel. This is due to biodiesel’s closed carbon cycle. The CO2 released into the atmosphere when biodiesel is burned is recycled by growing plants, which are later processed into fuel."


Translation: Biodiesel, like solar, generates 3 times the energy required to create it. The 78 percent figure cited by the DOE is probably assuming that fossil fuels were used to produce the biodiesel, which is totally unnecessary.

Ethanol is a bit more controversial. One estimate places the energy produced by making Ethanol at 1.67 times as much energy as required to produce it: www.usda.gov/agency/oce/oepnu/net%20energy%20balance.doc

while another source estimates that 71% more energy is required to produce a gallon of Ethanol than is contained within it: hubbert.mines.edu/news/Pimentel_98-2.pdf

Yet another report estimates a positive energy ratio of 1.37 for Ethanol and 3.2 for Biodiesel:
66.102.7.104/search
Note that the 1.37 figure for Ethanol in this report is highly dependent upon the increased crop yields for the corn crops studied in recent years and likely would not be obtainable without the use of pesticides.

In both the cases of producing biodiesel and Ethanol one should consider the costs of other inputs such as water. Some of these studies also include the energy content of pesticides, though why a pest free crop would be needed when it is not going to be eaten is not clear, unless the yield is a critical issue as it is with Ethanol.

Solar power requires a considerable investment in energy content as it takes 10 years of sun shining on a solar panel before the solar panel produces as much energy in the form of electricity as was required to create it. I was not able to find a reference to back up that information. But it seems obvious that solar electric panels produced from fossil fuel would not be an option if we suddenly run out of fossil fuel.