Particulate matter (PM) is released from mobile sources depending on the type of fossil fuel used in combustion. Long-term exposure to PM can affect both lungs and heart. According to the USEPA, PM exposure can cause a variety of problems like premature deaths, nonfatal heart attacks, irregular heartbeat, asthma, reduced lung function, and respiratory issues. Therefore, it is necessary to predict the downwind concentrations near highways for regulatory work. The current study concentrates on developing an analytical line source dispersion model for particulate matter in different particle size ranges. Available line source models do not consider explicitly different ranges of particle size present in the exhaust. The present study discusses the development of a dispersion model to predict downwind concentrations of PM by incorporating a range of particle sizes. The deposition of particles is also considered during development. Emission rate, wind speed, wind direction, atmospheric turbulence, and dry deposition velocity of the particles are the model inputs. The sensitivity of the model is determined by varying the independent input variables.