"Major trends affecting the future of the United States and the world will dramatically reshape transportation priorities and needs. The American Association of State Highway and Transportation Officials established the NCHRP Project 20-83 research series to examine global and domestic long-range strategic issues and their implications for departments of transportation (DOTs) to help prepare the DOTs for the challenges and benefits created by these trends. This publication is the sixth report in this series. This report presents the results of research on how socio-demographic changes over the next 30 to 50 years will impact travel demand at the regional level. The research approach involved identifying a number of plausible future scenarios and development of a systems dynamic model that simulates the demographic evolution of a regional population starting from a baseline of the 2000 census and spanning a period of 50 years. The four future scenarios were developed using a Strategic Assumptions Surfacing and Testing (SAST) technique and include the following: (1) Momentum: gradual change without radical shifts; (2) Technology Triumphs: technology solves many present-day problems; (3) Global Chaos: a collapse in globalism and sustainability, and (4) Gentle Footprint: a widespread shift to low-impact living. The model does not predict which scenario is most likely; instead it predicts how travel demand will change under each of the five sectors: socio-demographics, travel behavior, land use, employment, and transportation supply. The accompanying CD (CRP-CD-152) contains the Impacts 2050 software tool, the user's guide, a PowerPoint presentation about the research, and the research brief. The Impacts 2050 tool enables modeling of changes in these sectors due to socio-demographic changes, the interplay between sectors, and external factors such as attitudes and technology. This report will help transportation decision makers understand how the population may change over time, how socio-demographic changes will affect the ways people travel, and the kinds of transportation modes and infrastructure that will be needed."--Foreword.