Ambulance Diversion

Ambulance pulling out of hospital emergency area.

Ambulance diversion is a controversial strategy for temporarily relieving overcrowding in emergency departments (EDs).



What’s the Issue?

When a hospital invokes diversion status, incoming ambulances are directed to other facilities. As a response to ED congestion—first cited in a 1990 article in the journal Hospital Topics—less severely injured patients were transported to other nearby facilities.

At that time, ambulance diversion was viewed as a relatively rare option for coping with unexpected events or crises, but the phenomenon became a frequent occurrence over the next decade. In 2003, according to a 2006 study in the Annals of Emergency Medicine, 45 percent of EDs in the United States reported having gone on diversion status during the previous year, and in urban hospitals the rate was almost 70 percent. The study also reported that there were about half a million incidents of ambulance diversion in 2003—an average of about one per minute.

In the short term, ambulance diversion provides breathing room to the ED that invokes diversion status, allowing it to return to optimal functioning as it processes the overflow of patients. If the situation continues for an extended period, however, it can create a domino effect, triggering nearby facilities—now clogged with the diverted patients—to themselves go on diversion status. It can also lead to delays in medical care for patients elsewhere in the health care system. If an ambulance cannot bring people to the nearest facility, they have to be transported longer distances to receive necessary treatment. This increased travel time can reduce the availability of ambulances for new calls for other patients awaiting emergency medical service.

Despite these drawbacks, persistently high ED traffic has led to the continued use of ambulance diversion as a strategy for managing patient volume. “With the belief that ambulance diversion is a quick way to reduce hospital and ED overcrowding, many hospitals regularly use ambulance diversion,” noted a 2015 editorial in the American Journal of Emergency Medicine. “However, experts believe the practice does little if anything to reduce crowding; and research also suggests that diversion has negative patient care consequences.”

While research has linked ambulance diversion to delays in treatment and related indicators, such studies have often used diversion as a proxy for ED overcrowding. Given the many factors implicated in generating such conditions, experts generally consider restricting ambulance diversion, on its own, to be an ineffective and shortsighted strategy for addressing the problem. In recent years, studies from California, Massachusetts, and elsewhere have focused on efforts to reduce or ban ambulance diversion as part of comprehensive and coordinated approaches to alleviating ED congestion and improving patient flow, both within hospitals and among multiple facilities across a city or region.

What’s Next?

Ambulance diversion remains a critical issue at EDs across the country. Yet addressing it is complex because it is a symptom of the larger problem of ED and hospital overcrowding. Focusing solely on altering diversion strategies, therefore, might lead to temporary relief but is unlikely to resolve the overall problems that diversion is supposed to address. As recent research has shown, approaches to overcrowding that incorporate additional strategies alongside limitations on diversions are more likely to be effective in generating long-term changes. Moreover, greater regional communication and cooperation can minimize the likelihood of a domino effect that flips one hospital after another into diversion status.

In addition to seeking to improve patient care, hospitals recognize that they have a significant financial incentive to grapple with ambulance diversion, since sending patients away results in revenue loses. One study at an urban teaching hospital calculated that each hour of diversion was associated with a loss of more than $1,000 in revenue from patients brought by ambulance, while implementation of changes that limited diversion led to increased revenue of almost $200,000 a month. Yet widespread progress in mitigating diversion has not occurred.

The Affordable Care Act (ACA) did not include specific provisions about ambulance diversion. But the primary care system is not prepared to address the needs of the many millions of newly insured people, so EDs could see a continued increase in demand. Although the rise in urgent care centers could mitigate the impact, a recent post-ACA survey conducted by the American College of Emergency Physicians revealed a concerning statistic: 70 percent of respondents stated that their ED would not be adequately prepared for substantial increases in patient volume. Further research on the ACA’s impact on ED usage should help health care officials and administrators develop comprehensive policies to improve patient flow and reduce ambulance diversion that are appropriate for the new environment.