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The goal of any medical service is to provide the patient with the right resources at the right time. For many in our society any wait for anything is too long, hence the concept of a “Starbucks on every corner.”1 Although it is arguable that there is a greater need for emergency medical services (EMS) than for coffee, very few EMS agencies could afford to place an ambulance on every corner. Because of this EMS have used various deployment strategies to meet their patient care goals.

Deployment, according to one definition from the Free Dictionary, means, “To distribute (persons or forces) systematically or strategically.”2 Historically, ambulances were dispatched from fixed bases, most commonly from fire stations or funeral homes, depending on the local model. These stations were usually cited based on political subdivisions that have little or nothing to do with the needs of the community. In many areas, this practice continues today. In rural areas, and areas served by volunteer agencies, basing the ambulance at a station is the only system that makes sense. In urban areas, however, it is better to site equipment based on patient demand, rather than provider convenience. In these areas, as Overton and Gunderson have noted, the pattern of EMS usage resembles that of a police, rather than a fire department.3 Because of this, many high-volume urban organizations have adopted plans where ambulances are dispersed to predetermined “posts” around the service area. These posts may be a specific corner or perhaps a mall parking lot; in some cases the ambulance crew is given a general geographic area in which they are to be located. EMS agencies using this model of dynamic deployment are often described as “high performance” although this term may be a misnomer.


  • Define deployment and posting.

  • Describe the phases of ambulance response.

  • Describe how red-lights-and-siren responses affect the ambulance response.

  • Define system status management.

  • Describe the basic research concepts behind SSM.

  • Describe how technologies have changed SSM.


EMS systems have historically been designed to address two major ­problems: cardiac arrest and motor vehicle trauma. Spaite et al note that cardiac arrest accounts for a very small number of ambulance responses, and that there is no good data on the effects of EMS system ­components on trauma. He contends, “… Most prehospital trauma research has emphasized the wrong issues, asked the wrong questions, and used the wrong methods.”4 An attempt to rectify the lack of information on trauma patients demonstrated that there was no evidence supporting time sensitivity for trauma mortality.5 The problem, according to Spaite and his colleagues, is that EMS research has historically emphasized individual diseases and interventions, rather than system issues.

Many EMS agencies have a response standard written into their contract. Commonly such a clause says that the service ...

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