This report reviews and summarizes the current state of knowledge and practice related to mechanical damage in natural gas and hazardous liquid steel pipelines, with particular focus on transmission pipelines. Comprehensive voluntary interviews were conducted with 10 pipeline operators who represent a diverse cross section of industry professionals in the United States, Canada, and Europe. The interviews, which focused on operator practices for detection, characterization, and mitigation of mechanical damage on both gas and liquid transmission and gas distribution pipelines (the latter examined for comparison purposes), provided an invaluable source of data for the development of this report. Operator practices associated with prevention of mechanical damage primarily resulting from excavation damage were also extensively covered in the interviews.