The proportion of the United States population age 65 and over will increase significantly in the coming decades. The effects of aging on people as drivers and pedestrians are highly individual. Challenges that may impact people as they age include declining vision, decreased flexibility and psychomotor performance, and changes in perceptual and cognitive performance. Design practices that explicitly recognize these changes will better serve this growing segment of the nation's population. This Handbook for Designing Roadways for the Aging Population provides practitioners with a practical information source that links aging road user performance to highway design, operational, and traffic engineering features. This Handbook supplements existing standards and guidelines in the areas of highway geometry, operations, and traffic control devices. The information in this Handbook should be of interest to highway designers, traffic engineers, and highway safety specialists involved in the design and operation of highway facilities. In addition, this Handbook will be of interest to researchers concerned with issues of aging road user safety and mobility.