A 13-month study by the Dept. of Energy’s National Renewable Energy Laboratory, Golden, Colo., found that Class 8 tractor trailers’ fuel efficiency jumped 13.7% when powered by hybrid drives. (Class 8 trucks weigh over 33,000 lb. and include all tractor trailers.) The study’s hybrid trucks were equipped with 44-kW motors, lithium-ion battery packs, and regenerative braking. The study compared five hybrid and five conventional trucks of similar age used by Coca Cola Refreshments to deliver soft drinks in the Miami area. Researchers undertook the study to give truck-fleet operators an idea of how converting to hybrid drives can affect fuel efficiency.