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The first round of emissions testing of light-duty alternative fuel vehicles placed in the U. S. federal fleet under the provisions of the Alternative Motor Fuels Act was recently completed. This undertaking included 75 Dodge B250 vans, of which 37 were dedicated compressed natural gas models, and 38 were standard gasoline controls. Data were collected on regulated exhaust emissions using the federal test procedures, and on a number of other quantities, through a statistically controlled program of investigation. Fuel economy results were also recorded. All test vehicles were operated in routine federal service activities under normal working conditions, adhering as closely as possible to Chrysler's prescribed maintenance schedules. The data analysis conducted thus far indicates that the compressed natural gas vehicles exhibit notably lower regulated exhaust emissions, on average, than their gasoline counterparts, and that these values are well within U.S.

This study compares emissions test results among seven compressed natural gas and seven standard gasoline 1996 Ford Crown Victoria taxi cabs. The study applies a mixed-effects analysis of covariance (ANCOVA) model on data from three rounds of high-mileage emissions tests performed at target odometer readings of 60,000, 90,000, and 120,000 miles (i.e., 96,540, 144,810, and 193,080 km). The ANCOVA model describes emissions deterioration within each vehicle sample, while also accounting for individual vehicle variability within the sample. The model was used to determine whether there are statistically significant differences between each fuel's emissions profiles and deterioration rates over the mileage range studied. Results are reported for non-methane hydrocarbons, carbon monoxide, oxides of nitrogen, carbon dioxide, formaldehyde, and fuel economy.