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Background: There is uncertainty about how patients outside of endovascular-capable or Comprehensive Stroke Centers (CSC) access Endovascular treatment (EVT) for acute ischemic stroke. The role of the non-endovascular-capable Primary Stroke Centers (PSC) that can offer thrombolysis with alteplase but not EVT is unclear. A key question is whether average benefit is greater with early thrombolysis at the closest PSC before transportation to the CSC (Drip ‘n Ship), or with PSC by-pass and direct transport to the CSC (Mothership). Ideal transportation options for California, USA and Alberta, Canada were mapped based on the location of their CSCs and PSCs.Methods: For those who received both EVT and alteplase, probability models were developed from the ESCAPE trial’s decay curves for good outcome defined as mRS 0-2 at 90 days. To determine the benefits of alteplase alone, probability models were extracted from the Get-With-The-Guidelines decay curve. The onset to EMS arrival, time on scene, needle-to-door-out time at the PSC, door-to-needle-time (DNT) at the CSC, and door-to-reperfusion time were assumed constant at 30, 25, 20, 30, and 115 minutes, respectively. EMS transportation times were calculated using Google’s Distance Matrix API interfaced with MATLAB’s Mapping Toolbox to create maps demonstrating the transportation scenario resulting in the best outcomes. Six maps were generated for 30, 60, and 90 minute DNT’s at the PSC’s.Results: In the figure, green regions represent a greater probability of good outcome via Mothership, whereas red indicates that Drip ‘n Ship is best. Orange indicates that either option yields a similar outcome (+/- 2.5%). The color tint increases (becomes brighter) as the probability of good outcome decreases. Grey indicates areas with a sparse road network.Conclusions: The role of a PSC in close proximity to a CSC remains significant only when the PSC is able to achieve both a DNT of 30 minutes or less and a needle-to-door out time of 20 minutes.