FedEx Freight has begun beta testing two new tractors powered by Cummins Westport ISX 12 G liquefied natural gas-only engines.

The pre-production engine used in the new tractors is slated for limited release in 2013 and is currently the only all-natural-gas engine that begins to meet the size and power needs of Class 8 trucks, notes a company announcement. (The Westport HDT 15-liter uses a small amount of diesel.)

Domiciled at the FedEx Freight service center in Dallas, Texas, the tractors will be used as part of the carrier's regular linehaul operations and are expected to log nearly 1,000 miles per day. The extensive use will enable the company to quickly and thoroughly test the new engine's ability to meet the needs of day-to-day operations.

"FedEx Freight has a long-standing commitment to minimizing environmental impact, and natural gas-a cleaner burning fuel than diesel-has the potential to translate into lower greenhouse gas emissions," says John Smith, vice president of safety, fleet maintenance and facility services for FedEx Freight.

The LNG tractor beta test is part of a large-scale sustainability initiative by FedEx Freight to integrate responsible environmental practices into daily operations. Other efforts include:

- Experimenting with emission-free hydrogen fuel cell-powered and electric forklifts for dock operations.

- Equipping all new vehicles with SmartWay-approved tires that help improve fuel mileage.

- Fitting trailers with SmartWay-approved trailer skirts to improve aerodynamics and fuel consumption.