Patient Care, Rescue & Vehicle Extrication, Trauma

Automatic Crash Notification’s Role in Triage

Issue 1 and Volume 36.

The optimal way to reduce the consequences of injuries is to prevent them.(1,2) When injuries do occur, however, EMS providers must transport patients to the most appropriate health-care facility for the management of their injuries. Determining the destination facility can have a profound effect on the patient’s morbidity and mortality.

The National Study on the Costs and Outcomes of Trauma (NSCOT) evaluated the effect of trauma center care on mortality for severely injured patients. The study reported a 25% reduction in mortality for severely injured patients who received care at a Level I trauma center as compared with a non-trauma center.(3)

Determining the best destination hospital for an injured patient in an appropriate time frame (“right patient, right place and right time”) is the primary goal of successful field triage. This is also an area in which vehicle telematics and Advanced Automatic Collision Notification (AACN) can play a significant role.

Automatic Notification
Vehicle telematics is the integration of wireless communication into a vehicle’s electrical architecture, which allows a vehicle and its occupants to interact and communicate with other vehicles, the road, public safety answering points (PSAPs) or telematics service provider call centers.(4,5) A component of vehicular telematics, AACN, is the successor to Automatic Crash Notification (ACN) and is found in an increasing number of motor vehicles.

When a vehicle’s AACN system detects a crash (as determined by vehicle sensors, airbag deployment or seatbelt pretensioners), either an urgent message is directly relayed to the local PSAP or the vehicle’s Global Positioning System (GPS) location and crash-related data—change in velocity (delta-V), principal direction of force, airbag deployment, multiple collisions and rollover determination—are automatically sent by emergency wireless call to a telematics service provider.

These methods allow injured occupants to communicate in real-time with PSAPs or the telematic service provider emergency call centers without having to initiate the call.

AACN in Field Triage
The Centers for Disease Control and Prevention (CDC) and the American College of Surgeons-Committee on Trauma, with additional financial support from the National Highway Traffic Safety Administration (NHTSA), convened a series of meetings of the National Expert Panel on Field Triage to guide the 2006 revision of the Triage Decision Scheme. During these meetings, panel members discussed the potential for vehicle telem­atics to more accurately guide trauma triage decisions.

In earlier versions of the Field Triage Decision Scheme, a number of vehicle crash characteristics were incorporated into the prehospital triage decision evaluation as “mechanism of injury” criteria. These included, among others, high vehicle speed, vehicle deformity greater than 20 inches and intrusion greater than 12 inches for unbelted occupants. But the usefulness of these criteria, as well as that of vehicular speed, were limited because of the challenges EMS providers face when accurately estimating damage to vehicles and impact speed.(6)

Today, however, AACN technology not only identifies a vehicle’s location but also measures velocity, detects principal direction of force, determines airbag deployment and identifies the occurrence of multiple collisions or rollover.(4,7) These crash characteristics, when compared with existing data, have the potential to provide information on the likelihood of severe injury and, in many cases, enable EMS systems to allocate the appropriate resources—such as ALS, rescue and aeromedical assets—to the scene earlier than in the past. They also have the ability to better prepare emergency departments and trauma centers for severely injured patients.

As a result, and in recognition that this information will likely become more available and widespread in the future, “vehicle telemetry data consis­tent with a high risk for injury” was added as a triage criterion.

Optimizing the Use of AACN
In follow up to the need to further explore how AACN could improve triage, the CDC selected and convened an additional expert panel. Its purpose was to develop a medical protocol for utilization of AACN data from crashes and use this information to improve the ability to respond to crashes and appropriately triage crash patients.

This panel included representation from the following disciplines: PSAPs (9-1-1 call centers) EMS, emergency medicine, trauma surgery, engineering, public health, vehicle telematics providers, NHTSA and the Health Resources and Services Administration’s EMS for Children program.

The expert panel met three times and developed an initial model protocol for use with AACN (See Figure 2 at They also made several conclusions and recommendations regarding the future of AACN.(8) The full AACN report is available at

The committee said the available information strongly supports immediate use of vehicle telemetric data in field triage decision guidelines. Also, AACN shows promise in improving outcomes in severely injured crash patients by predicting the likelihood of serious injury in vehicle occupants and decreasing response times by prehospital care providers. It also assists with field triage destination and transportation decisions, decreases time to definitive trauma care and decreases death and disability from motor vehicle crashes.

The committee said that current AACN data transmitted from the vehicle to the telematics provider can improve accuracy in triage of the injured patient. They recommended that because seatbelt use by an occupant significantly influences injury severity, information regarding seatbelt use should be included in AACN data transmission. The committee also recommended that AACN providers obtain specific occupant information that’s known to alter or influence injury severity and to significantly influence response to injury, including age and gender.

Further refinement of key data elements will require ongoing investigation and data analysis. Also, AACN data haven’t been previously used in clinical decision-making, so pilot studies should be implemented as soon as possible using the following protocol.

In the event of a crash, the following electronic information should be transmitted by the vehicle to the AACN providers:
> Change in velocity (delta-V);
> Principal direction of force (PDOF);
> Seatbelt usage;
> Crash with multiple impacts; and
> Vehicle type.

This information would be received by the AACN provider and analyzed to identify those patients who, based on the data alone, have risk of severe injury that’s greater than or equal to 20%, defined as an injury severity score (ISS) greater than 15. If the analysis indicates the risk of severe injury is less than 20%, then the AACN provider proceeds per standard protocol.

If the AACN data analysis indicates a risk of severe injury greater than or equal to 20%, the AACN provider directly contacts the vehicle occupant to obtain more information.

During communication with the occupant, the AACN provider will inquire about the following data:

  • Age (Patients who are 55 years old or older have increased risk of
  • severe injury.);
  • Injuries sustained by vehicle occupants;
  • Number of injured occupants; and
  • Number of vehicles involved.

This information may help refine the AACN data adjusting the likelihood that a severe injury has occurred. For example, if the occupant is able to communicate clearly that they’re uninjured and less than 55 years of age, then the risk of severe injury is lessened. Similarly, if there’s no voice appropriate response from the occupant, if the occupant is 55 years old or older or if they indicate an injury, then the risk of severe injury remains at least 20% (based on the AACN data alone) and is potentially greater.

The committee also noted that if the AACN provider determines that the occupant is at least 20% likelier to sustain severe injury, then providers should communicate with the relevant Public Safety Answering Point (PSAP) that AACN data obtained from the vehicle indicates that the occupant is at risk for a severe injury. The PSAP should dispatch resources as appropriate according to local protocol and consistent with the Field Triage Decision Scheme: The National Trauma Triage Protocol.(4)

Another note was if the AACN data indicate that the risk of injury is less than 20% and the AACN provider subsequently obtains occupant information that raises concern for a severe injury (e.g., injuries and age), then this specific information can be communicated to the PSAP.

According to the committee, AACN providers will also communicate the following information to the PSAP, when available:

  • Age of occupant(s);
  • Presence of one or more injuries based on voice communication;
  • Number of other vehicles involved, if any; and
  • Location confirmation or disparity between electronic and voice
  • communication.

The committee recommended a national system should collect and analyze AACN and injury data. This should be integrated as much as possible into current national data systems (e.g., the National Accident Sampling System (NASS), the National Emergency Medical Services Information System (NEMSIS) and the National Trauma Data Bank (NTDB)).

They stated that the feasibility of AACN providers acquiring components of the Glasgow Coma Scale through voice communication with vehicle occupants and transmitting that information to PSAPs (or 9-1-1 call centers), EMS and receiving
hospitals should be investigated further.

Also, a study should investigate what AACN data best predicts a need for extrication, and a system of real-time communications should be established between all components of the trauma system, including AACN providers, PSAPs (or 9-1-1 call centers), EMS, emergency medicine and trauma surgery.

AACN systems show great promise in improving field triage of an injured patient. Vehicles equipped with these systems are increasingly present on our nation’s roadways, and the data provided can have a profound effect on determining the severity of injury, ensuring an appropriate EMS response and preparing our hospitals to manage and care for patients injured from car crashes.

With a wide range of vehicle manufacturers and telematics service providers transmitting AACN information, collaboration is essential to ensure standardization. Continued cooperation is critical to ensure consistent information is being transmitted to emergency care systems and personnel. Further study, including pilot projects and research, is necessary as AACN continues its integration in our nation’s vehicles. JEMS


  1. 1. Sasser S, Varghese M, Kellermann A, et al, editors: Prehospital Trauma Care Systems. World Health Organization: Geneva, 2005.
  2. 2. Sasser S, Varghese M, Joshipura M, et al. Preventing death and disability through the timely provision of prehospital trauma care. Bulletin of the World Health Organization. 2006;84:507.
  3. 3. MacKenzie EJ, Rivara FP, Jurkovich GJ, et al. A national evaluation of the effect of trauma-center care on mortality. NEJM. 2006;354:366–378.
  4. 4. Ball WL. Telematics. Prehosp Emerg Care. 2006;10:320–321.
  5. 5. National Highway Traffic Safety Administration.
  6. 6. Sasser SM, Hunt RC, Sullivent EE, et al. Guidelines for field triage of injured patients. Recommendations of the National Expert Panel on Field Triage. MMWR Recomm Rep. 2009;58:1–35.
  7. 7. Hunt RC. Emerging communication technologies in emergency medical services. Prehosp Emerg Care. 2002;6:131–136.
  8. 8. Centers for Disease Control and Prevention National Center for Injury Prevention and Control.

This article originally appeared in January 2011 JEMS as “The Future Is Now: How Advanced Automatic Collision Notification can assist in the early response, triage & care of injured patients.”