Homeland Security Presidential Directive (HSPD)-5, Management of Domestic Incidents, directed the development and administration of the National Incident Management System (NIMS). Originally issued on March 1, 2004, by the Department of Homeland Security (DHS), the National Incident Management System (NIMS) provides a systematic, proactive approach to guide departments and agencies at all levels of government, nongovernmental organizations, and the private sector to work seamlessly to prevent, protect against, respond to, recover from, and mitigate the effects of incidents, regardless of cause, size, location, or complexity, in order to reduce the loss of life and property and harm to the environment.
The NIMS Incident Command System (ICS) provides clear procedures for coordinating between agencies and on-scene responders and outlines roles and activities assigned to each. Who fills the role of Incident Commander is usually dictated by the nature of the call and the level of command experience of the responders. For example, on an injury accident scene that requires extrication of a patient, it is common for a fire/rescue officer to serve as Incident Commander. On a spilled load or other incident that impacts traffic flow but does not involve life/safety threats, a law enforcement officer may perform the command function. On complex incidents with multiple response agencies, Unified Command is used to coordinate between the agencies and provide a management structure for the incident. ICS recognizes that different disciplines may need to assume the role of Incident Commander at various stages of the incident, and provides for an orderly transfer of command as assignments are completed.
Law enforcement, in cooperation with other incident participants shall be responsible for securing the incident scene in a manner to safely make available the most travel lanes as soon as reasonably possible. As specialized resources such as fire and rescue EMS, and towing and recovery complete their missions, they will clear the incident and return to their normal duties. This will also be true of law enforcement and other agencies as they complete their required functions, and it is determined their resources are no longer needed. The paramount goal is restoring the roadway to normal traffic as soon as possible.