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UPS Study Rates the Reliability, Low Emissions of CNG Trucks

A large study comparing trucks fueled by natural gas with others fueled by diesel found the natural gas vehicles produced only a quarter of the carbon-monoxide emissions and half the oxides of nitrogen emissions of their diesel counterparts.

The study was conducted using package trucks operated by United Parcel Service, which has the nation's largest private compressed natural gas (CNG) fleet. The study compared the operations, maintenance, performance, and emissions characteristics of Connecticut-based CNG and diesel vehicles from 1997 to 2000, as part of the broader U.S. Department of Energy/National Renewable Energy Laboratory Truck Evaluation Project. In addition to volunteering use of its package trucks for the study, UPS staff worked closely with NREL during the study.

The CNG trucks ran every working day with no major complaints and were used as much or more than the diesel trucks.

Compared with diesel truck emissions, CNG truck carbon monoxide emissions were 75% lower, oxides of nitrogen 49% lower, hydrocarbons and non-methane hydrocarbons 4% lower, and carbon dioxide 7% lower.

Total operating costs of CNG trucks were 2% lower than total operating costs of diesel trucks at one of the study sites and 19% higher at the other site.

Because the CNG trucks were built with early production technology, they had a 27% to 29% lower energy equivalent fuel economy than diesel trucks. Newer technology can reduce this deficit to as low as 10% to 15%.

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