Photo by Greg Aragon for ENR

Komatsu's 22-ton PC200LC-8 Hybrid Excavator, which went on sale earlier this year, is the first hybrid of its kind in the U.S.

The California Air Resources Board is studying the effects of two pieces of hybrid construction machinery, the Caterpillar D7E bulldozer and Komatsu PC200LC-8 excavator, under a $2-million grant at the University of California, Riverside.

The two-year project aims to analyze the emissions profiles of the hybrid machinery and develop incentive programs for contractors to use them, researchers say.

"Hybrid construction vehicles are just now becoming available," says Kent Johnson, as assistant research engineer at the school's Center for Environmental Research and Technology. "We have been asked to use our emissions testing experience to quantify what their benefit is."

Half the grant will fund vouchers to push 20 to 30 hybrid machines into the field. The other half will fund testing of six vehicles scattered throughout the state.

Manufacturers say hybrid machines cut fuel consumption by 20% to 30% compared to their non-hybrid equipment. However, they come with a higher price tag, costing 20% or more.

Last year, CARB decided to delay rules to curb emissions of existing off-road equipment until 2014. Previous to that action, industry groups complained that construction firms had parked equipment during the economic downturn and, as a result, were emitting less than previously believed.