This paper examines how transit riding fundamentally affects consumer responses to mobile ads. On the basis of theoretical frameworks on time perception (Hornik and Zakay 1996), we illuminated the contextual particularity of temporal captivity. By analyzing field experiment data from a large mobile payment provider, we identified that ad receptivity among mobile users is higher under captive transit conditions. We also found that passenger targeting can foster greater enhancement in ad effectiveness when additional temporal conditions are achieved. Temporally proximal distribution from boarding, long travel times, time instability, and contingent deviations to routine positively moderate stronger contextual effects. Further analysis revealed that those moderators operate differently between routine and non-routine travel routes. Our results accord with the theoretical intuition drawn from the time perception framework. Researchers and practitioners can equally benefit from our findings given that they expand the purview of context-based targeting and provide wide-ranging opportunities for effective advertising.