Area navigation (RNAV) and required navigation performance (RNP) are key components of performance-based navigation (PBN). Instrument procedures that use RNAV and RNP can have more flexible and precise paths than conventional routes that are defined using ground-based navigation aids. As a result, RNAV and RNP routes can enhance operational safety, efficiency, and access. At the United States Department of Transportation Volpe Center, we are identifying and documenting human factors issues associated with implementing PBN instrument procedures for the Federal Aviation Administration (FAA). This effort supports the FAA's transition to the Next Generation Air Transportation System (NextGen) by providing recommendations to promote easier and more reliable use of PBN instrument procedures. In this paper, we explain why human factors research is needed and provide examples of research issues. For example, new procedures may result in increased visual complexity of charts, which in turn could increase pilot workload and the potential for error. We are also conducting analyses and experiments to understand and improve the usability of aeronautical charts for PBN instrument procedures. Our work in this area is summarized in this paper. More information can be found at www.volpe.dot.gov/coi/hfrsa/ahf/ip/library.html. The website has links to our latest research products. It also supports other human factors research teams by listing and summarizing publicly available reports on related topics.