The traffic density for an urban interstate highway is 10,000 vehicles/hr and the average vehicle speed is 40 km/hr. The wind speed perpendicular to the highway is 4 m/s. The average carbon monoxide emission per vehicle is 10 g/km. (a) For an overcast day, estimate the CO concentrations 0.02, 0.05 and 0.1 km downwind from the highway. (b) Do the concentrations found in part (a) represent a health hazard based upon the 1-hr CO NAAQS?

Use the Briggs formula for the dispersion parameter.