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CARBON MONOXIDE EXPOSURES INSIDE AN AUTOMOBILE TRAVELING ON AN URBAN ARTERIAL HIGHWAY
Citation:
Ott, W., P. Switzer, AND N. Willits. CARBON MONOXIDE EXPOSURES INSIDE AN AUTOMOBILE TRAVELING ON AN URBAN ARTERIAL HIGHWAY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/476 (NTIS PB95138285).
Description:
Carbon monoxide (CO) exposures were measured inside a motor vehicle during 88 standardized drives on a major urban arterial highway, El Camino Real (traffic volume of 30,500-45,000 vehicles per day), over a 13-1/2 month period. n each trip (lasting between 31 and 61 minutes), the test vehicle drove the same 5.9-mile segment of roadway in both directions, for a total of 11.8 miles, passing through 20 intersections with traffic lights (10 in each direction) in 3 California cities (Menlo Park, Palo Alto, and Los Altos). arlier tests showed that the test vehicle was free of CO intrusion. or the 98 trips, the mean CO concentration was 9.8 ppm, with a standard deviation of 5.8 ppm. f 9 covariates that were examined to explain the variability in the mean CO exposures observed on the 88 trips (ambient CO at 2 fixed stations, atmospheric stability, seasonal trend function, time of day, average surrounding vehicle count, trip duration, proportion of time stopped at lights, and instrument type), a fairly strong seasonal trend was found. odel consisting of only a single measure of traffic volume and a seasonal trend component had substantial predictive power (R2 = 0.68); by contrast, the ambient CO levels, although partially correlated with average exposures, contributed comparatively little predictive power to the model. he CO exposures experienced while drivers waited at the red lights at an intersection ranged from 6.8 ppm to 14.9 ppm and differed considerably from intersection to intersection. odel also was developed to relate the short-term variability of exposures to averaging time for trip times ranging from 1 to 20 minutes using a variogram approach to deal with the serial autocorrelation. his study shows: (1) the mass balance equation can relate exterior CO concentrations as a function of time to interior CO concentrations, (2) CO exposures on urban arterial highways vary with season, (3) momentary CO experienced behind red lights vary with the intersection, and (4) an averaging time model can simulate exposures during short hips (20 minutes or less) on urban arterialhighways.
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CARBON MONOXIDE EXPOSURES INSIDE AN AUTOMOBILE TRAVELING ON AN URBAN ARTERIAL HIGHWAY