Detailed hydrocarbon and aldehyde mobile source emissions from roadway studies.
A field study was conducted along US Highway 70 near Raleigh, NC, to evaluate methods for estimating emission factors and, in particular, for determining volatile organic carbon (VOC) species emitted from traffic. Integrated samples were collected 1m from the roadway between 7:30 and 8:30 a.m. at four different roadside locations representing various combinations of traffic conditions. The light-duty traffic component (>90%) was classified by model year between 1975 and 1983. On a percent of total non-methane basis,the distribution of VOC's varied little between sampling sites. The roadside VOC distribution was compared to dynamometer/dilution tube test results on in-use vehicles, which were weighted to reflect the same model year distribution observed on the roadway. Some of the differences seen were attributed to fuel effects, while others may reflect an insufficient data base. Mass emission rates calculated from release of a tracer gas by a pace car varied unpredictably and were higher than those calculated by the Mobile3 model or observed with the in-use vehicle dynamometer data.