A recent report from the National Research Council will help guide the federal government as it develops fuel-economy and carbon regulations for medium- and heavy-duty trucks. Congress is looking at this group of previously unregulated vehicles because they use 26% of the liquid transportation fuel consumed in the U.S., and their energy consumption is projected to continue rising for the next 25 years. The 414-page report shows that combining such technologies as advanced diesel engines, hybrid powertrains, improved aerodynamics, low-resistance tires and others could improve fuel economy in work vehicles by as much as 50% by 2035. The cost of
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.