This volume provides a background of actual design error cases in different engineering discipline as a basis for methods for avoiding and identifying design error in volume 3 and 4. It describes the types of errors, error causality, and statistics of error occurrence. Examples of the design errors are given, the most famous from accident reports from sources such as the US National Transportation Safety Board, US Chemical Safety Board, and similar sources from around the world. Many of the examples are from the author's own experience from safety audits, design review supervision and accident investigations. Many design error type are repeated in all engineering discipline, though some have quite specific forms, such as bridge collapse through scouring, or process plant accidents due to runaway chemical reactions. Virtually all design errors though are detectable and preventable, once it is recognized that like any human activity, design is subject to errors and failures. For each error type, the possibilities for avoidance, identification by design review and by error identification are summarized, with detailed description of methods given in Volumes 3 and 4.