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FTP-UDDS (urban dynamometer driving schedule) exhaust particulate matter (PM) emission rates were determined for 361 light-duty gasoline (LDGV) and 49 diesel passenger vehicles ranging in model year (MY) from 1965 to 1997. LDGVs were recruited into four MY categories. In addition, special effort was made to recruit LDGVs with visible smoke emissions, since these vehicles may be significant contributors to the mobile source PM emission inventory. Both light and heavy-duty diesels where included in the passenger diesel test fleet, which was insufficient in size to separate into the same MY categories as the LDGVs. Vehicles were tested as-received in three areas: Denver, Colorado; San Antonio, Texas; and the South Coast Air Quality Management District, California. The average PM emission rates were 3.3, 79.9, 384 and 558 mg/mi for 1991-97 MY LDGVs, pre-1981 LDGVs, smoking LDGVs and the diesel vehicles, respectively.

The light-duty diesel vehicle has been targeted for some years as a contributor to the visibility problem in many urban areas. The Colorado Department of Health. Air Pollution Control Division, has conducted a pilot inspection/maintenance program for the purpose of evaluating the effectiveness of a loaded mode inspection program in reducing diesel opacity and particulate emissions levels. The study consisted of screening approximately 200 vehicles using a loaded mode test cycle and exhaust opacity measurements to select a test population of 13 vehicles. Those vehicles exceeding a given opacity standard were subjected to the Federal Test Procedure (FTP) both before and after repairs. The vehicles subsequently underwent a series of maintenance sequences.

This paper discusses five vehicle emissions testing programs conducted by the Colorado Department of Health (CDH) to evaluate “gasohol” (a mixture of 10% ethanol and 90% gasoline, by volume) as a potential CO reduction strategy for high altitude locations. These testing programs included: Forty-seven 1978-1983 passenger cars. Five 1982 “high mileage” passenger cars. Two passenger cars (one 1984 and one 1985) with reported “adaptive learning” capabilites. Eleven 1979-1984 passenger cars tested at sub-FTP temperatures. Eight non-catalyst light and heavy-duty trucks. Mass emissions levels of hydrocarbon, carbon monoxide and oxides of nitrogen were measured during these test programs. In addition, the forty-seven vehicle study also includes fuel economy and driveability comparisons when using gasoline and gasohol.

Increasingly stringent Federal exhaust emissions standards being applied to new automobiles necessitates an accurate short test to indicate vehicle emission failures for Inspection Maintenance (I/M) Program purposes and to trigger the Emission Control System Warranty provided in Sections 207 (a) and 207 (b) of the Clean Air Act. It was the intent of the Colorado Department of Health to develop a test that would accurately identify excess exhaust emissions and have an acceptable mathematical correlation to the results of the Federal Test Procedure (FTP). In an attempt to decrease the errors of omission exhibited by existing short tests, a short loaded mode, mass emissions test was considered. A basic statistical analysis of the EPA Urban Dynamometer Driving Schedule was performed and a 226 second driving schedule was developed. This driving schedule was entitled the CDH-226. The CDH-226 has been performed on one hundred seventy six (176) 1981-1984 in-use vehicles at high altitude.