This report studied person throughput as an impact metric for proposed BRT routes under Caltrans jurisdiction, given the agency’s specific interest in preserving or improving the performance of particular state-owned corridors. It also introduces a simple spreadsheet tool to estimate a BRT project’s traffic impact and show how improved bus service can boost corridor performance. Representatives of Caltrans D4, D7, and D11 were interviewed after tentative development of the tool, expressed support of a transition towards person throughput, and offered feedback on how the tool might best suit most district employees’ needs.