Bill Vlasic:

While American consumers were taking advantage of low gas prices to buy trucks and sport utility vehicles in large numbers, some automakers delayed investing in slower-selling electrified vehicles.
 But with increases in federal fuel-economy standards looming in 2017, car companies are hustling to bring out hybrid and electric models to help them meet the new rules — even though electrified vehicles make up only 2 percent of overall sales.
 The federal government has mandated corporate average fuel economy of 54.5 miles per gallon by 2025. But companies need to meet an interim standard of about 37 m.p.g. by next year.