Traffic is the predominant source of pollution in urban cities like Delhi. Continuous monitoring of the air quality in roads will be very costly and impracticable. To carry out model calculations is a useful alternative to measuring. The most crucial parameter of models is the source strength, which can be estimated in many ways. In the present study, four different methods of source estimation of vehicular traffic, have been proposed. These methods have been evaluated by means of an air quality model, i.e. IIT Line Source (IITLS) model. The ground level concentrations of NO2 have been obtained from IITLS model in which emission rates have been calculated by using these methods. The IITLS model’s predictions have been compared with observed concentrations of NO2 at two vulnerable places in Delhi. The performance of these methods have been tested through five statistical performance measures. It has been observed from above study, that IITLS’s predictions of air pollutants with first three methods of emission estimation are in agreement with observed levels and also well correlated. Thus first three methods are considered to be appropriate for emission estimations of NO2 due to vehicular traffic. On the basis of availability of traffic data, method 3 has been found most suitable for Indian urban cities. The same methods may be used for other gaseous pollutants CO, HC, SO2 and particulates Lead (Pb) and SPM.