The U.S. Environmental Protection Agency and the U.S. Dept. of Transportation have put forth the first national standards to cut greenhouse-gas emissions and raise the fuel efficiency of heavy-duty trucks and buses. The proposal, which the agencies announced on Oct. 25, would apply to work vehicles ranging from large, heavy-duty pickup trucks in Class 2b to the largest Class 8 tractor-trailer trucks, weighing 80,000 lb or more. The EPA and DOT action follows a directive issued by President Obama. The benchmarks would kick in for vehicles manufactured in model years 2014 through 2018. EPA and DOT estimate the standards will
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.