Dwell time at a bus stop is one of the major components of bus travel time, and it is highly correlated with numbers of boarding and alighting passengers. With more resources from federal, state, and local governments currently being devoted to improving public transit services, transit ridership rates are expected to increase. Consequently, dwell time needs to be modeled in terms of ridership to allow accurate estimations of bus travel time. Typically, passengers can board a bus only through the front door but can choose to exit the vehicle through either the front or rear door. To estimate dwell time accurately, this study used data collected from Florida's Broward County Transit system to develop a binary door choice model predicting the proportion of alighting passengers who will use the front or rear door to disembark from the bus. Because the model explicitly considered passengers disembarking through the front and rear doors as well as passengers boarding through the front door, it was more effective in quantifying transit dwell time than the existing simulation algorithms available in CORSIM and VISSIM.