There are many potential energy conservation and emission reduction strategies. Which
are best? Which deserve the greatest support? Some provide significant co-benefits and
avoid undesirable, unintended consequences and so provide greater total benefits. In
general, a gallon of fuel conserved by reducing vehicle travel provides an order of
magnitude more benefit than the same energy savings provided by shifts to more efficient
or alternative fuel vehicles. This occurs because mileage reductions provide other
economic, social and environmental benefits, such as reduced traffic congestion, facility
costs, accidents and sprawl. Many mobility management programs are justified for their
economic benefits and so provide essentially free environmental benefits. In contrast,
increased vehicle fuel efficiency tends to stimulate more total vehicle travel, which
exacerbates other transportation problems: emissions decline but congestion, parking
costs, accidents and sprawl increase.