To improve airport ground access at Taoyouan International Airport (TIA) in Taiwan, the government of Taiwan is constructing a mass rapid transit system (TIA MRT) to connect the airport and important traffic hubs such as the Taipei train station and the Taoyouan High Speed Rail station. Using revealed and stated preference data, we investigate the airport ground access mode choice behavior of air passengers who are traveling overseas from Taiwan. A mixed logit model is estimated to identify the preferences of air passengers for the new mode. The results indicate that while out-of-vehicle travel time and in-vehicle travel time are two important factors in affecting outbound travelers' choice of airport access mode, the amount of overall time-savings and the user-friendly nature of the modal offers are also crucial attributes. We show the extent to which travel time improvements associated with public transportation reduces the market share of private transportation and taxi.