The objective of this study was to obtain a better understanding of CO concentrations immediately upwind of urban roadways, the "local background" values, and how these concentrations depend upon the surrounding traffic and the general meteorology. Measurements were made at seven sites during the winter of 1993. Local background CO concentrations were characterized by an absence of short term fluctuations, a steady buildup during the period between 3:00 PM and 11:00 PM, and a lack of spatial gradients in the eight-hour average values. Distinctly different log-normal distributions of the eight-hour averages were observed for "trafficked" sites versus "urban park" sites, with mean values of 1.6 and 1.0 ppm respectively. A simple regression model was developed to predict the local background CO. This regression model included distance from the roadway, average daily traffic on nearby roadways, and the frequency of low wind speeds (R2=0.74;F=170). A new CO sampler was also developed as a part of this project.