A quantitative, rapid screening assessment methodology for masonry arch bridges, with minimal input parameters, is proposed. The developed mechanism-based analysis procedure is validated against a set of available experimental data. Performance levels are then prescribed for bridges falling into proposed subsets based on geometric proportions. A generalized amplification factor (κ) is introduced, which could account for an increase in demand due to a dynamic vehicle-bridge interaction as well as an increase in axle loads. Finally, fragility curves are generated, which gives the probability of collapse for a bridge subset against increasing demand parameter. © 2021 American Society of Civil Engineers.