They can now reach 70 percent efficiency. Their numbers are expected to grow by tens of millions as Chinese, Indians, and Brazilians begin to lead versions of Western lifestyles. So more efficiency on the road is a must - in terms of resources as well as climate change. We've noted with interest recent announcements by Honda, Toyota, and Saab of new super-efficient engines. That's important, because California has hit a setback in selling consumers zero-emission electric cars.
Prices are still too high and trips between chargings to short to woo many buyers.
For such cars to become standard, they will have to be reliable enough and cheap enough to attract mass buyers. That means Western consumers buying enough to bring about economies of scale. Then versions for mass markets in developing lands. None of this is simple.