MIT report on future of transportation

with comprehensive focus on automotive technology choices.   very helpful in understanding the different characteristics of different types of engine technologies.

report here:  Fueling our Transportation Future

money quote from the summary:

"We have concluded that a 30–50% reduction in fuel consumption is feasible over the next
30 years. In the short-term, this will come as a result of improved gasoline and diesel engines
and transmissions, gasoline hybrids, and reductions in vehicle weight and drag. If these
improvements are achieved, we estimate a $1,500–$4,500 increase in vehicle costs. Over the
longer term, plug-in hybrids and later still, hydrogen fuel cells may enter the fleet in numbers
sufficient to have significant an impact on fuel use and emissions."