UPS said its fleet is an ideal framework for testing new technologies to reduce emissions from heavy-duty trucks. The carrier is working with several engine manufacturers to test viable options approved by the Society of Automotive Engineers.

"With the introduction of liquefied natural gas tractors, we now operate alternative fuel vehicles in every part of our fleet," said Ron Kirby, corporate automotive engineering manager for UPS.

According to UPS, preliminary data shows the new LNG tractors, while substantially more expensive, address four concerns: providing ample power to tractors hauling over-the-road trailers while still significantly reducing emissions, maintenance and operating costs.