Browsing College of Engineering and Mines (CEM) by Author "Johnson, R.A."
Implementation of CALINE4Johnson, R.A.; Anderson, M.; Lilly, E.; Hok, C. (1988-11)To help gauge the environmental impacts of proposed highway projects, computer models are commonly used to predict both CO emissions and the resultant concentrations of CO in the atmosphere. This study has focused on an assessment of MOBILE3 as a mobile source emissions model and CALINE4 as a line source dispersion model in Alaska. We have used limited data obtained in Fairbanks o evaluate CALINE4 here. We have modified MOBILE3 to allow it to predict emissions at ambient temperatures below 0(degrees)F and have incorporated available meteorological data for Fairbanks to evaluate CALINE4. We find the use of these models does allow one to approximate trends over time in CO levels in Fairbanks, but a lack of more detailed data precludes our being able to make global statements about the abilities of the models to predict peaks and detailed spatial trends. However, the results to data indicate that these models have the potential to accurately predict CO levels in Alaska. In particular, results from a 37-hour calibration run made near an intersection indicates that CALINE4, using emissions generated by MOBILE3, can predict peak one-hour and eight-hour values within a factor of two of measured values. Conservative peak value predictions occur when the intersection option is used with the wind blowing from the intersection toward the receptor. However, the nonmodeled CO contributions may be significant if only major roads near a receptor are modeled. For worst case predictions, the limited data analyzed corroborates prior work linking worst case scenarios with cold stable meteorological conditions. In particular, a G stability case and wind speed around 0.5 m/s are appropriate. We also suggest the receptor be located downwind from an intersection. For the input emissions, we suggest the use of MOBILE3 using an average vehicle speed of 20 mph and a temperature around -20(degrees)F for Fairbanks and 10(degrees)F for Anchorage. For ambient CO levels, we suggest the user consult with local environmental agency personnel.