This article offers a brief summary of the articles in this special issue, plus it provides a rationale for the scientific study of urban bus operation. Among the reasons to study urban transit operators are the following: Multimethodological, international data show that urban bus driving is an unhealthy occupation; psychosocial and environmental characteristics of the transit work setting portend ill health, plus these characteristics are readily discernible to the public; urban transit workforces well represent blue-collar populations; despite widespread changes in the nature of work related to technological innovations, mass-transit operation is likely to remain stable, and the "health" of the mass-transit industry has important implications for societal well-being; and finally, bus driving illustrates several important methodological challenges. The article concludes with an overview of future research.