With automakers struggling to stay afloat, fuel prices rising again and a federal directive looming to clean up greenhouse-gas emissions, President Obama unveiled a plan to increase average fuel-efficiency standards for passenger cars and light trucks by up to 41% by 2016. Starting in model-year 2012, the vehicles will need to meet increased mile-per-gallon ratings, eventually reaching 39 mpg for cars and 30 mpg for trucks. Current regulations require an average 35 mpg by 2020. The rule, which aims to reduce imports of foreign oil, cut costs for motorists and reduce tailpipe exhaust under one national standard, is a landmark
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.