The U.S. government's push to decrease the nation's output of greenhouse gases by increasing the fuel efficiency of the cars Americans drive is arousing again an emotional argument: Does driving a small, fuel-efficient car make you more likely to die on the road? Engineers and statistical analysts can point to data that suggest more-efficient cars don't necessarily put motorists at greater overall risk. But most of us care less about the "overall" risk than we do about ourselves. Driving a big Chevrolet Tahoe SUV makes many of us believe we are safer than we would be in a smaller car -- even if statistical measures across a large population of vehicles and all kinds of car accidents suggest the advantage of safety isn't quite as wide as SUV owners believe. The Obama government has put the fuel-efficiency and safety question back on the front burner by calling for new-vehicle fuel economy to rise to an average of 35 miles per gallon   by 2020 from about 25 mpg today. That goal could move higher if the government decides to adopt California's requirement to cut vehicle greenhouse-gas giving off, which would result in stricter mileage standards. Those moves, and the effects of last summer's gas-price shock, are driving auto makers to offer cars such as the Toyota Yaris, Honda Fit and Daimler AG's Smart For Two -- which get the kind of mileage today that law says should be the average in a decade. Beyond that, auto makers will launch a wide range of new compact   vehicles, and decrease production of large, body-on-frame SUVs. That's leading to new concerns about "green safety", a term for managing the balance between reducing vehicle size for efficiency and adding safety and protection features that tend to make vehicles heavier and less efficient. Undoubtedly, further work has to be done before Americans make the choice. About the Obama government's new moves, the auto makers are   _   and average
uncertain; positive doubtful; uncertain supportive; positive positive; uncertain