["Oxford Bulletin of Economics and Statistics, EarlyView. ", "\nABSTRACT\nThis paper examines how alternative surcharge designs affect market outcomes in the New York City (NYC) Yellow Cab system. We study two distinct policies: a congestion surcharge that raises passenger fares without directly compensating drivers, and a rush‐hour surcharge that provides time‐based incentives to drivers during periods of high demand. Using a regression discontinuity in time framework, we exploit discrete changes in fares to identify the causal effects of these surcharges on trip volume. We find that the congestion surcharge reduces demand for short‐distance trips but does not generate measurable improvements in traffic conditions, suggesting a shift in trip composition rather than effective congestion mitigation. In contrast, the rush‐hour surcharge leads to an immediate increase in trip volume at the policy threshold, consistent with a supply‐side response to driver incentives. Although both policies increase fares, they operate through distinct economic mechanisms and are identified from different sources of variation. Our findings highlight that the effects of fare increases depend critically on policy design‐specifically, whether pricing operates as a tax on passengers or as an incentive for drivers. More broadly, the results underscore the importance of distinguishing between demand‐ and supply‐side channels when evaluating pricing interventions in regulated transportation markets.\n"]