Vehicle intrusion crashes in highway work zones injure vehicle occupants and workers alike, and such crashes are the concern of both state agencies and highway contractors. This paper describes the results of an effort to develop prototypical scenarios of common work zone intrusion crashes documented in the New York State Department of Transportation work zone accident database. A prototypical scenario can be defined as one that is representative of the crash process because of the typicality of its chain of events and the likely causal relationships throughout the stages of the crash. By considering the chain of events that led to a particular crash, it is possible to group similar crashes and provide a more in-depth assessment, even though some of the facts involved in the individual crashes vary. In the study described here, prototypical scenarios were developed for four intrusion crashes at four types of work zone operations: lane closures, flagging operations, mobile operations, and traffic control setup and removal activities. It was concluded that a significant portion of intrusion crashes resulted from deliberate driver decisions and actions to enter the work space. The frequency of such deliberate events, which ranged from 25% to 64%, depended on the type of work operation in place on a given roadway. The study identified between three and eight prototypical crash sequences that were not the result of deliberate actions by drivers and that led to intrusion crashes.