To address emergency department overcrowding operational research seeks to identify efficient processes to optimize flow of patients through the emergency department. Vertical flow refers to the concept of utilizing and assigning patients virtual beds rather than to an actual physical space within the emergency department to care of low acuity patients. The aim of this study is to evaluate the impact of vertical flow upon emergency department efficiency and patient satisfaction. Prospective pre/post-interventional cohort study of all intend-to-treat patients presenting to the emergency department during a two-year period before and after the implementation of a vertical flow model. In total 222,713 patient visits were included in the analysis with 107,217 patients presenting within the pre-intervention and 115,496 in the post-intervention groups. The results of the regression analysis demonstrate an improvement in throughput across the entire ED patient population, decreasing door to departure time by 17 min (95% CI 15–18) despite an increase in patient volume. No statistically significant difference in patient satisfaction scores were found between the pre- and post-intervention. Initiation of a vertical split flow model was associated with improved ED efficiency.