Many accidents involve questions regarding human visual performance. For example, drivers involved in accidents often report that they did not see what they hit, or that they saw it too late to do anything. In these cases, it is often necessary to determine if people or objects at the accident scene (pedestrians, motorcycles, other vehicles, debris, etc.) would have been visible to the reasonably alert person under conditions of a particular accident. This determination must be made with proper consideration of both inter- and intra-person variabilityThe goal of accident reconstruction is to determine what happened in an accident, and why it happened. This process involves a thorough examination of the available evidence. More specifically, the investigator considers the physical evidence, accident reports, and statements of the involved parties and witnesses. The investigator applies the principles of physics to define a set of accident scenarios that are consistent with the available evidence. This approach often falls short of explaining what happened, as there may not be a unique accident scenario that is consistent with all of the evidence. Furthermore, the question of why the accident happened may not be addressed at all by analysis of the physical evidence alone, as almost all accidents are influenced by the performance of the people involved in the accident. Human performance issues such as vision, attention, and distraction, often play a large role in why an accident happens.The purpose of this paper is to illustrate the value of considering issues of vision and visibility when reconstructing an accident. Illustrative examples from actual accidents will be used throughout.