As the U.S. population ages, so will the population of licensed drivers. Policymakers are concerned that this will lead to increases in traffic accidents and, consequently, injury to property and person. Although the capacity to safely operate a motor vehicle decreases at older ages, at least some older individuals voluntarily limit their driving when they perceive that their ability to drive has diminished. Do the elderly self-regulate enough that their overall negative impact on traffic safety is no more than that of other drivers? The research reported in this volume estimates how the probability of causing an automobile accident varies with age. Findings include that older drivers are somewhat more likely than middle-aged ones to cause an accident, but the bigger issue may be that they are much more likely to be injured or killed if they are in an accident, regardless of fault.