Recently, focus on the analysis of public transit systems has been increasing. The "Transit Capacity and Quality of Service Manual" consolidates information on current practices. By stating that no national studies support transit capacity analysis for demand-responsive operations, the manual identifies an inability to estimate capacity and level of service for agencies that provide demand-responsive transit. A procedure for calculating a serviceability index (SI) for demand-responsive transit operators based on regional socioeconomic conditions and internal operation data is presented. The methodology results from a survey of several demand-responsive transit providers in Alabama and data analysis. A case study for two counties served by the Northwest Alabama Council of Local Governments transit agency illustrates the SI calculation to identify benefits and drawbacks. Generated with input from transit providers, SI can be used to evaluate and compare demand-responsive transit operation.