This document provides guidance recommendations and supporting material to assist designers and implementers of intelligent transportation system (ITS) applications related to highway-rail intersections (HRI). The guidance focuses specifically on roadway user human factors requirements associated with ITS as applied to HRIs. The guidance is intended to be of immediate help to practitioners but also to serve as a resource and impetus toward the development of consensus standards and other more formal guidance or specification. The document has four parts. Part I describes the purpose and scope and provides a human factors conceptualization of the roadway user. Part II provides an overview of ITS applications that have been implemented at HRIs. Part III presents general human factors guidance that cuts across various specific HRI applications, for topics such as message factors, roadside displays, in-vehicle displays, and displays for pedestrians. Part IV presents guidance for specific HRI applications, including train arrival warnings, advance information about the HRI, enforcement and control of vehicles, and light rail transit. Each guidance chapter provides background on the topic, an explicit statement of the major human factors issues, and a set of guidance recommendations (with accompanying rationale for each). This report includes over 130 guidance recommendations.