Next year, Chevrolet and GMC will offer new bi-fuel versions of the 2015 Chevrolet Silverado and GMC Sierra heavy-duty trucks as well as the all-new dedicated compressed natural gas versions of the 2014 Chevrolet Express and GMC Savana full-size passenger vans.

The vehicles were announced at the Green Fleet Conference & Expo, which focuses on clean technologies and alternative-fuel vehicles for fleet operations.

“With these new vehicles, General Motors offers the most comprehensive lineup of manufacturer-engineered, validated and warranted CNG vehicles, helping fleet managers manage their budget and reduce their carbon footprint,” said Ed Peper, U.S. vice president, GM fleet and commercial sales. “Natural gas is less costly at the pump and significantly reduces carbon dioxide emissions, compared to other liquid fuels.”

The bi-fuel versions of Silverado HD and Sierra HD – which are equipped to run on either gasoline or natural gas – expand the range of available configurations to 2500HD and 3500HD pickup models in all cab styles and 2WD and 4WD drivetrains, according to GM.

The 2014 Express and Savana passenger vans join a dedicated CNG lineup that includes cargo versions of the vehicles, says GM.

The CNG fuel tanks and complementing fuel systems used in the trucks and vans are installed by GM’s tier one supplier at a secondary location and delivered to customers from Chevrolet and GMC dealerships. The vehicles are fully warranted and validated by GM.

“These vehicles meet the rigorous GM standards for safety, reliability and durability,” said Peper. “They’re backed by a comprehensive five-year/100,000-mile transferable powertrain limited warranty, too, meaning we back these vehicles for the long haul.”

Production for the bi-fuel trucks and CNG vans is scheduled to begin early next year, says GM.