Atmospheric/plume turbulence parametrization is an important input for the estimation of dispersion of pollutants from the vehicular exhaust. A Three-Phase Turbulence (TPT) model was proposed by Madiraju and Kumar (2021) considering the critical parameters such as initial vertical plume spread, downwind distance, wind velocity, additional spread due to vehicular wake, thermal turbulence, atmospheric turbulence, road width, residence time and mixing height of mobile source dispersion. The flow regime of the TPT model is divided into the initial phase, transition phase, and dispersion phase. The current study considers the use of line-source and area-source using the TPT model for dispersion of exhaust. The paper will present the performance of these two types of modeling approaches based on the current practice using dispersion curves from point sources and the new TPT model. The statistical indicators (including model bias (MB), fractional bias (FB), normalized root mean square error (NMSE), correlation coefficient (r), geometric mean bias (MG), geometric variance (VG)) are used as a performance measure to identify the variations in the model results using observed data from three different field studies. The study will identify the better modeling approach (line-source versus area-source). The changes in the performance of simple mobile source models with the use of the TPT model are observed.