There is a persistent need for improved tools and techniques to facilitate public involvement in transportation decision making. Despite continuous improvements in increasing public involvement at all phases of transportation decision making, transportation agencies are still seeking more affordable, accessible, and effective means of communicating with a wide range of stakeholders. The report documents a survey of a wide variety of transportation agencies on their use of interactive 3-D visualization for public involvement using an electronic survey. Supplemental qualitative data was generated through telephone interviews with selected survey participants. It concludes with three case studies illustrating applications of interactive 3-D visualization to support public involvement in transportation decision making. The report concludes that the use of interactive 3-D mapping, although pervasive in transportation planning and design, is at the early stages of application as a public involvement tool. Most agencies use the tools for the purposes of informing stakeholders, illustrating the location of proposed projects, or plans or programs of projects in a regional or study area context, but not for engaging them in a specific dialogue in a meeting, workshop, or on-line chat forum.