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Emissions from heavy-duty vehicles may be reduced through the introduction of clean diesel formulations, and through the use of catalyzed particulate matter filters that can enjoy increased longevity and performance if ultra-low sulfur diesel is used. Twenty over-the-road tractors with Detroit Diesel Series 60 engines were selected for this study. Five trucks were operated on California (CA) specification diesel (CARB), five were operated on ARCO (now BP Amoco) EC diesel (ECD), five were operated on ARCO ECD with a Johnson-Matthey Continuously Regenerating Technology (CRT) filter and five were operated on ARCO ECD with an Engelhard Diesel Particulate Filter (DPX). The truck emissions were characterized using a transportable chassis dynamometer, full-scale dilution tunnel, research grade gas analyzers and filters for particulate matter (PM) mass collection. Two test schedules, the 5 mile route and the city-suburban (heavy vehicle) route (CSR), were employed.

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.

The first round of emissions testing of flexible fuel methanol vehicles from the U.S. federal fleet was completed in 1995. The vehicles tested include 71 flexible fuel M85 1993 Dodge Spirits, 16 flexible fuel 1994 M85 Ford Econoline Vans, and a similar number of standard gasoline Dodge Spirits and E150 Ford Econoline Vans. Results presented include a comparison of regulated exhaust and evaporative emissions and a discussion of the levels of air toxins, and the ozone-forming potential (OFP) of the measured emissions. Three private emissions laboratories tested vehicles taken from the general population of federal fleet vehicles in the Washington D.C., New York City, Detroit, Chicago, and Denver metropolitan regions. Testing followed the standard U.S. Environmental Protection Agency's Federal Test Procedures (FTPs) and detailed fuel changeover procedures as developed in the Auto/Oil Air Quality Improvement Research Program.

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.