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The Colorado Department of Health (CDH) collected CO exhaust emissions data from twenty-one vehicles using three “short” emissions tests, and the Federal Test Procedure (FTP). CO data were also collected from these vehicles using a remote sensing system. Excess carbon monoxide emissions were calculated from the difference between FTP measurements and federal standards. Emissions were then categorized by individual vehicle and by vehicle type. Errors of comission and omission were determined for each of the short tests and remote sensing system. The CDH226 showed the highest correlation for identifying vehicles emitting excessive CO. Compared to the FTP, it identified the vehicles responsible for 98.5% of all excess emissions. All the “short” tests and remote sensing tests identified the vehicles producing the majority of excess emissions. The current BAR '84 type idle “short” test and the CDH226 demonstrated the lowest errors of comission, or false failures.

Vehicle age distribution is an important consideration when evaluating the effects of exhaust emissions. To quantify CO idle data from motor vehicles of different model year groupings and vehicle classifications, the Colorado Department of Health (CDH) reviewed emissions data from The Colorado Automobile Inspection and Readjustment (A.I.R.) Program. Colorado's A.I.R. Program is presently in its 9th year and is considered a mature I/M (inspection maintenance) Program. (1) Program data from December 1989, January 1990 and February 1990 were studied to determine the mean % CO by vehicle class and model year group. Classes include: light duty, heavy duty and mixed light and heavy duty (fleet) vehicles. Model year groups include: 1974 and older, 1975-1980, 1981-1982, and 1983 and newer model year vehicles. The 10% highest CO emitting vehicles (by CO emission concentration) in these categories were also evaluated.

Diesel particulate emissions are less than 2.5 micron. This size range particulate are major contributors to visibility-related problems in both urban and rural areas, as in the Denver Brown Cloud. Diesels are currently estimated to make up 10 to 20 percent of Denver's haze. Particulates in the diesel size range are also inhalable, capable of traveling deep into the lungs and being retained for long periods of time. As diesel particulates contain large quantities of organic materials, long term health effects from exposure to diesel particulates are of concern. It is estimated a diesel I/M Program will reduce diesel particulates from affected vehicles by 10 percent. Proposed changes would impact all diesel motorists and owners who have diesel motor vehicles registered or principally operated along Colorado's Front Range.

The winter of 1988-89 marked the second program year of the Colorado Oxygenated Fuels Program. As part of that program, the Colorado Department of Health (CDH) conducted a study to determine the environmental and economic impacts of the use of oxygenated fuels. For use in that study, the U.S. EPA contracted for a cost analysis of the program which was conducted by RCG/Hagler Bailly, Inc. The CDH study, with the assistance of the EPA contract study, looked at the air quality benefit and exhaust emission reductions, economic cost, market distribution of available oxygenated fuels, and public education and enforcement activities for the Oxygenated Fuels Program. The findings of this study were previously released in the report, “1988-89 Oxygenated Fuels Program - Air Pollution Control Division Final Report to the Colorado Air Quality Control Commission” (AQCC).

Many parts of the country have been in violation of the carbon monoxide and ozone National Ambient Air Quality Standards. Because of these violations, vehicle inspection and maintenance (I/M) programs have been implemented throughout the country. A method and procedure of evaluating the benefits of an I/M program as compared to the projected benefits designated in the MOBILE3 Emission Factor model has been developed. The method includes a detailed analysis of the individual operating parameters of an I/M program, such as the vehicle population, waiver procedures, and manual vs. automated analyzers. Evaluation of these parameters can assist agencies to compare benefits of their I/M programs to those projected in MOBILE3. This is of major importance, due to the requirements of the 1987 deadline for carbon monoxide and ozone attainment and the “reasonable extra efforts” program which undoubtedly will be required by EPA.

Recent regulatory attention has focussed on reducing the emissions from new heavy-duty diesel vehicles. Stringent new NOx and particulate emissions standards will go into effect in 1988 and 1991. The long lifetimes of heavy-duty trucks and buses, the high levels of emissions per vehicle, and the acute particulate problems in many cities all argue that retrofitting emission controls to existing vehicles should be considered as well. This paper presents a preliminary evaluation of eight potential diesel retrofit technologies (considered as any technique for reducing emissions from existing vehicles). Technologies considered were (in order of their apparent promise): diesel fuel modifications, trap-oxidizers, conversion to methanol fuel, particle agglomerators, fumigation with LPG, vertical exhausts, special-purpose fuel additives, and high-altitude adjustments/kits. The technical feasibility, emissions benefits, approximate cost, and cost-effectiveness of each technique are discussed.

This paper provides an overview of Colorado's efforts to reduce particulate emissions from light- and heavy-duty vehicles. As a result of the passage of Senate Bill 193, Colorado has enacted several programs to control diesel emissions. These programs include a roadside opacity enforcement program, a pilot light-duty inspection program, and a public education program. Colorado is in the process of setting up Emissions Technical Centers for purposes of supporting the diesel opacity enforcement program. Currently, they are developing light- and heavy-duty test procedures. Colorado is planning numerous diesel related activities in the future. They will be investigating the relation between opacity and mass emissions, in order to better define correlation between the two indicators. CDH also will be performing much more research into test cycles and will be investigating a light- and heavy-duty I/M program. Considerable amounts of data will be available by next fall.

Automobiles and other mobile sources are a major contributor to precursors of ozone and to carbon monoxide in urban area air pollution inventories. In a typical urban area, over fifty (50) percent of the emissions of hydrocarbons (HC) and of oxides of nitrogen (NOx), which react in the presence of sunlight to form ozone, are derived from vehicular sources. Over ninety (90) percent of the carbon monoxide emissions in these areas are also attributable to mobile sources. This problem is accentuated in the Front Range Region of Colorado, due to the higher altitude. The Colorado Automobile Inspection and Readjustment (AIR) Program was designed and implemented in an effort to reduce the contributions to ambient air pollution from mobile sources. The intent of this study is to evaluate whether there is a difference in the effectiveness of the Colorado AIR Program on the major technological groups of emissions control configurations.

The AIR Program has been in full operation in the Front Range counties of Colorado since January 1, 1982. Data from the first 477,905 vehicles tested indicate an average reduction in idle tailpipe carbon monoxide (CO) concentration for re tested vehicles of 56%, while the reduction for hydrocarbons (HC) averages 42%. This represents a reduction of approximately 151 tons of CO per day. The average cost of adjustments for 1968 to 1980 vehicles has been $9.23 and the average repair cost for 1981 and newer vehicles has been $22.30.