Proximity Matters: The Impact of Collocated Urgent Care Center on Emergency Department Arrivals

The use of urgent care centers (UCCs) to reduce emergency department (ED) overuse has yielded mixed results in prior research. This paper investigates how the spatial proximity between UCCs and EDs drives heterogeneous effects of UCCs on ED demand. Using novel, granular encounter-level data from both newly opened UCCs and EDs within a major medical system, we leverage exogenous variation driven by institutional UCC operating hour policies to estimate causal effects. Through difference-in-differences models with unit-specific quadratic trends and generalized synthetic control methods, we find that collocated UCCs reduce ED demand for initial patient visits, with reductions spanning both nonurgent and urgent encounters. In contrast, non-collocated UCCs do not reduce ED demand. Such a difference is statistically significant. We identify queue sampling as the key mechanism driving these heterogeneous effects. Using timestamped arrival data, we show that higher ED waiting room census leads to increased arrivals at collocated UCCs, but only when the waiting room reaches visibly congested levels—in our setting, the top quintile of census distribution. This suggests patients exploit minimal switching costs to avoid observable congestion. This dynamic substitution pattern is absent at non-collocated sites, where transportation costs inhibit real-time facility switching. Our work sheds light on UCC location decisions and patients’ facility choice behavior in an era of rapid UCC market expansion. For hospital managers, we show that when reducing ED demand is a primary objective, opening UCCs collocated to EDs proves substantially more effective than establishing them elsewhere in the region. For policymakers, while current UCC siting discussions focus primarily on expanding geographic access, our results demonstrate that carefully considering UCCs' spatial configuration relative to EDs can unlock additional operational benefits beyond long-term access improvements.