... variablesfor month of the year, day of the week, hour of the day, and interactions between weekends andhour of the day. Overall, the results are consistent with the results presented above.One potential ... responsible for a substantial portion of total emissions. Of the vehicles surveyed, half of all carbo n monoxide emissions are derived from 24% of t he fleet andhalf of hydrocarbon emissions ... Specifications include weather covariates and indicator variables for month of the year, day of the week and hour of the day, as well as interactions between weekends and hour of the day. The R2for the...