Impact of ambulance diversion policies in urban, suburban, and rural areas of Central Maryland

Acad Emerg Med. 2001 Jan;8(1):36-40. doi: 10.1111/j.1553-2712.2001.tb00546.x.


As a method to control patient flow to overburdened hospitals, effective emergency medical services (EMS) systems provide policies for ambulance diversion. The Maryland state EMS system supports two types of alert for general hospital use: red alert, aimed at limiting the delivery of patients who may require intensive care unit (ICU) admission, and yellow alert, aimed at preventing further overload of already overtaxed emergency departments (EDs).

Objective: To examine the effect of those alert policies in different geographical environments, urban, suburban, and rural.

Methods: Alert data for 23 hospitals in Central Maryland and ambulance arrival data for approximately 138,000 ambulance calls during calendar year 1996 were combined and analyzed. The impacts of diversion practices in the geographic areas were compared.

Results: Red alert reduced volume in all patient acuity levels in all geographic areas by a statistically significant 0.4 patient/hr. Yellow alert diverted low-acuity patients at the rate of 0.13 patient/hr (p<0.001) in urban areas and at the rate of 0.16 patient/hr (p<0.001) in suburban areas, but had minimal impact in the flow of patients in the rural environment.

Conclusions: The ED diversion policy has some limited effect in preventing further patient volume in urban and suburban areas, but has virtually no impact in rural areas. However, an ICU diversion policy diverts patients of all acuities uniformly and inordinately diverts patients not likely to require ICU admissions while having only minimal impact on patients who do require ICU resources. The impact of red alert is uniform in all geographic areas. The impact and efficacy of ambulance diversion policies should be evaluated to ensure they are having the intended effect. While perhaps initially effective, the impact of alert policies may change over time.

MeSH terms

  • Ambulances / organization & administration*
  • Ambulances / statistics & numerical data
  • Emergency Medical Services / organization & administration*
  • Emergency Medical Services / statistics & numerical data
  • Humans
  • Maryland
  • Retrospective Studies
  • Rural Population
  • Suburban Population
  • Urban Population