increase in vehicle density). Since there is a much smaller increase in vehicle density, the emission reduction/vehicle is less. This represents the high end of the allowable emission range, shown below. In summary, the required automotive emission control to achieve primary air quality standards is: Since high ambient NO2 values are primarily a problem of the Southern California area, it would be possible to satisfy the primary air quality standards with two levels of Similar controls are shown for HC and CO for both California and non-California vehicles, since "Present Air Quality" shows a similar range in both areas. · 12 RECENT EPA UPDATE OF ROLLBACK CALCULATIONS (9) The opinion that the Barth paper was a poor basis for setting 1975 emission standards, and additionally that the 1975 standards are a poor translation of the Barth results, is substantiated by a recent report from EPA. This report, which was included as Appendix I-F in the February 28, 1972 report on the Cumulative Regulatory Effects on the Cost of Automotive Transportation (RECAT), concludes with the emission reduction as percent, and the resulting standards as follows: Note that by these EPA calculations, the 1975/76 standards are too lenient for HC, but too stringent, by factors of 2.5 to 3, for CO and NOx. The calculated Standard for HC is very low because of the high ratio assumed for the production of oxidant from HC. (Not in accord with current information, see Appendix C). The calculation of emission reductions required to meet desired air quality standards, and the resulting standards for motor vehicles, is a scientific route to proper controls. It should be preferred to an arbitrary 90 percent further reduction from partially controlled 1970 vehicle sources. REFERENCES 1. 2. Barth, D. S., "Federal Motor Vehicle Emission Goals for "National Primary and Secondary Ambient Air Quality Standards," 3. McGraw, M. J., and Duprey, R. L. "Compilation of Air Pollutant Emission Factors," Preliminary Document, p. 24, Environmental Protection Agency, Research Triangle Park, N.S., (April 1971). 4. From Figure 6-7 of HEW CO Criteria document (AP-62). Chicago data have been excluded because as shown in Attachment 2, data for the years 1964-66 are suspect. 5. 6. 7. 8. Air Quality Criteria - Nitrogen Oxides AP-84 Air Pollution Stanford Research Institute Report "Sources, Abundance and The HC level is a conservative background level based on data in the HEW Hydrocarbon Air Quality document (AP-64). "General Assessment of the Air Pollution Problem and Philosophy Underlying Automotive Emission Controls" for presentation to the Office of Science and Technology Ad Hoc Committee on the Costs of Automotive Transportation, by J. C. Romanovsky, Technical Advisor to the Director, National Environmental Research Center, EPA. 9. Stern, Arthur C., "National Emission Standards for Stationary Sources", Journal of the APCA, August, 1970. "Attachment A-1" is taken from a reference cited by Barth in his paper, which apparently was used to arrive at the desired 90 percent reduction mandate of the 1970 Clean Air Act Amendments. Landsberg's projections of vehicle population were made in the early 1960's and reflected population projections of the 1960 census. More recent projections of vehicle population, which reflect data from the 1970 census have been made by the U. S. Department of Transportation in August, 1970. These projections are presented in Attachment A-2. The Landsberg and DOT projections are compared in Figure A-1. Growth factors from the two have been calculated and are shown in Figure A-1. It is well known that large urban centers grow by expansion of their peripheral areas. Local downtown growth does not keep up with the national projections. Rather, a saturation in traffic density is reached, and continued growth of density lags behind total vehicle growth in an area. Data on urban vehicle growth predictions is presented in "Attachment A-3". Table 1 of this attachment reveals that while the continued trend to progressive urbanization will produce large increases in total vehicles in that area, the downtown vehicle density will increase at a much slower rate. - 2 Growth Factor as Related to Carbon Monoxide from Automotive Sourc Air pollution is principally a problem of large urban areas. In particular, carbon monoxide levels reflect the density of the motor vehicle population, as well as power plants in other industrial sources. Downtown Chicago and central New York City are areas where high ambient air CO levels have been observed. The highest present air quality (uncontrolled) values for CO were found in these cities. According to Table I of Attachment A-3, the traffic density predicted by 1980 for New York and Chicago shows essentially zero change. For this reason the growth factor in density of motor vehicles, or CO sources, is essentially zero. A growth factor of 1.0 is therefore indicated. Many other large cities show a projected increase in traffic density of about 10%. This would correspond to a growth factor of 1.1 From the above information it is concluded that a growth factor of 1.0 to 1.1 is an adequate representation of the increase in traffic density, which is closely related to maximum carbon monoxide levels. Thus, a range in growth factor from 1.0 to 1.66 is used in the calculation of the carbon monoxide rollback required. The lower end of this range is considered much more representative of the real situation. This results in CO emission standards of 20.2 to 22.2 grams/mile. |