Performance evaluation of CALINE 4 dispersion model for an urban highway corridor in Delhi

Abstract

The paper focuses on the performance evaluation of CALINE 4 model for predicting carbon monoxide (CO) concentrations along an urban highway corridor passing through the city of Delhi. The model was applied using two different sets of Indian emission factors for different categories of vehicles specified by Central Pollution Control Board (CPCB), and Automotive Research Association of India (ARAI) in conjunction with on-site traffic and micro-meteorological inputs. The modelling results indicate that the dispersion of CO along the corridor was limited to a distance of ~150m from the edge of the mixing zone width (road width+3m on each side of the road). The concentrations were found to be 12% higher in the case of ARAI emission factors as compared to the CPCB emission factors. The correlation coefficient values (r²) between predicted and observed 1-hour concentrations for CPCB and ARAI emission factors were found to be 0.60 and 0.65 respectively. In addition, the estimated index of agreement (d) values of 0.86 and 0.85 respectively indicate satisfactory model performance. However, the estimated fractional bias (FB) values of 0.04 for CPCB and 0.06 for ARAI emission factors indicate that the CALINE 4 model under predicts the concentrations in both the cases.