What Is a Trauma System?
A trauma system is an organized, coordinated effort in a defined geographic area that delivers the full range of care to all injured patients and is integrated with the local public health system. The true value of a trauma system is derived from the seamless transition between each phase of care, integrating existing resources to achieve improved patient outcomes. Success of a trauma system is largely determined by the degree to which it is supported by public policy.
Trauma systems are regionalized, making efficient use of health care resources. Trauma systems are based on the unique requirements of the population served, such as rural, inner-city, urban, or Native American communities. Trauma systems must emphasize the prevention of injuries in the context of community health. Ultimately, nationwide development of trauma systems would allow for seamless and effective care across the United States with the ability to expand to meet the medical needs of the community from a man-made or natural disaster.

What Is a Regional Trauma Center?
What Is Trauma?
The trauma patient is an injured person who requires timely diagnosis and treatment of actual or potential injuries by a multidisciplinary team of health care professionals, supported by the appropriate resources, to diminish or eliminate the risk of death or permanent disability. Injuries occur across a broad spectrum and a trauma system must determine the appropriate level of care for each type of injury.

http://www.nhtsa.dot.gov/people/injury/ems/emstraumasystem03/index.htm

Definitions
The four levels refer to the kinds of resources available in a trauma center and the number of patients admitted yearly. These are categories that define national standards for trauma care in hospitals. Developed and recommended by the American College of Surgeons.

Level	Description
I	A Level I trauma center has a full range of specialists and equipment available 24-hours a day and admits a minimum required annual volume of severely injured patients. Additionally, a Level I center has a program of research, is a leader in trauma education and injury prevention, and is a referral resource for communities in nearby regions.
II	A Level II trauma center works in collaboration with a Level I center. It provides comprehensive trauma care and supplements the clinical expertise of a Level I institution. It provides 24-hour availability of all essential specialties, personnel and equipment. Minimum volume requirements may depend on local conditions. These institutions are not required to have an ongoing program of research or a surgical residency program.
III	A Level III trauma center does not have the full availability of specialists, but does have resources for the emergency resuscitation, surgery and intensive care of most trauma patients. A Level III center has transfer agreements with Level I and/or Level II trauma centers that provide back-up resources for the care of exceptionally severe injuries.
IV	A Level IV trauma center provides the stabilization and treatment of severely injured patients in remote areas where no alternative care is available.