Purpose This paper describes a benchmarking framework applied to medium-sized urban public bus agencies in the United States, which has overcome the challenges of data quality, comparability, and understanding. Design/methodology/approach The benchmarking methodology described in this paper is based on lessons learned through seven years of development of a fixed-route key performance indicator (KPI) system for the American Bus Benchmarking Group (ABBG). Founded in 2011, the ABBG is a group of public medium-sized urban bus agencies that compare performance and share best practices with peers throughout the United States. The methodology is adapted from the process used within international benchmarking groups facilitated by Imperial College and consists of four main elements: peer selection, KPI system development, processes to achieve high-quality data, and processes to understand relative performance and change. Findings The four main elements of the ABBG benchmarking methodology consist of 18 subelements, which when applied overcome three main benchmarking challenges: comparability, data quality, and understanding. While serving as examples for the methodology elements, the paper provides specific insights into service characteristics and performance among ABBG agencies. Originality/value The methodology, while consistent with recommendations from literature, is unique in its scale, in-depth validation and analysis, and holistic and multidimensional approach.