This study is concerned with estimation of the probable shift of car users to bus due to increase in its level of service after providing exclusive bus lanes on Indian city roads carrying heterogeneous traffic. The quantum of increase in level of service of bus due to introduction of exclusive bus lane was determined using a recently developed simulation model of heterogeneous traffic flow. The data of the other factors (variables) that might cause modal shift from car to bus were collected through home-interview survey based on the stated preference approach. A binary Logit model of mode-choice was then calibrated using the collected data and the model was also validated using holdout sample. Through this study, a set of causal factors, with reliable and predictable data base, to explain the variation in shift behaviour of personal vehicle users to buses consequent on the increase in the level of service of buses, has been identified. A mode-choice probability curve to depict the possible modal shift of car users to bus is developed, taking the difference in travel times of the two-modes as the basis, to serve as a user friendly tool to analyze the possible modal shift for a wide range of values of the involved variable.