Understanding Emergency Department Wait Times

Executive Summary

Emergency departments (EDs) operate as the gateway to many acute care hospitals. Patients who arrive at the hospital through the ED will often experience long wait times of 3-4 hours on average.1 Excessively long wait times lead to higher health risks, patients leaving the ED without being treated, ED overcrowding, and low patient satisfaction. The root causes of wait times are complex and affected by many factors within and beyond the ED. The issue of overcrowding in waiting rooms delays treatment for individual patients and reduces the efficiency of patient flow from the ED to inpatient wards. One main cause for the long wait times observed in the ED is that non-emergent patients are coming to and being treated in these settings. Some of the challenges inherent in ED wait times are discussed in this article, with links to relevant tools and case studies provided.

  • Background on Emergency Department Overcrowding
  • Triage System
  • Clinical Decision Unit
  • Keeping Patients Vertical
  • Lean Process and Tools
  • Key Takeaways


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Background on Emergency Department Overcrowding

Overcrowding occurs when service providers and processes function at a slower rate than the frequency of new patients arriving to the ED. When the supply of resources cannot match demand for service, patients experience lower quality care, worse health outcomes, and they report poor satisfaction.

The waiting time in EDs can be more or less be categorized into three components: (1) Door to doctor, (2) Doctor to disposition, and (3) Disposition to departure. The amount of waiting time from the moment the patient enters the ED to the moment they see a physician is the greatest factor that determines patient satisfaction. It has been found that the majority of time spent in the ED by patients is ‘processing time’ before they even get to see a physician.

Frequently, patients who visit the ED have non-urgent illnesses or injuries. One U.S. study found that over 50% of ED visits were non-urgent cases that could be treated in a different setting. To solve this issue, better methods of identifying and reassigning these patients to appropriate health care departments and optimizing waiting rooms according to patient conditions must be established. As health insurance in many countries becomes increasingly expensive and the need for primary care providers widens, the need to address overcrowding in EDs grows.  

Triage System to Sort and Prioritize Patients

Emergency Departments encounter patients everyday with a wide range of severity of illness and injury. As a result, the triage process is a vital part of the ED workflow to sort and prioritize urgent patients for treatment. Ineffective or unorganized triage systems result in patients not being able to see their physician in the recommended amount of time, as demonstrated in the chart below:


The triage system can be optimized using the Rapid Clinical Examination/ Rapid Medical Evaluation (RCE/RME) technique. Currently, it is common that triage occurs at registration or by a specially trained health care provider following registration. Memorial Health Center used the RCE process to achieve reduced average length of stay (LOS) and the number of patients who leave without treatment (LWOT). A defining characteristic of RCE is that patients who visit the ED see a physician who immediately evaluates whether they are an emergent (stroke, chest pain, trauma, etc.) patient or non-urgent patient who can be sent back to the waiting area. Memorial saw a 68% reduction in LOS of admitted patients and a 50% reduction in LWOT. Further information is available in the following case study:

Standardization of the triage system among ED health care providers is also an important technique for improved efficiency. To ensure all nurses, clinicians, and physicians use the same terminology and guidelines to sort patients, Hillcrest Hospital implemented the Emergency Severity Index (ESI). With ESI staff training and a split-flow model that treats urgent and non-urgent patients separately, Hillcrest successfully reduced LOS and LWOT. An additional technique was utilized to provide each staff member with a laminated ESI Implementation Handbook to help staff identify the different triage levels:.  

Clinical Decision Unit for Low Acuity Patients

Emergency Departments are overcrowded partly because there isn’t enough physical space to treat all patients. A potential solution to this problem is to physically differentiate the waiting area for patients under different circumstances. One method of differentiation is to separate critical patients and non-critical patients in waiting rooms for treatment. Waiting rooms can even be physically distinguished into different ‘zones’ for patients at different points in the waiting process. Furthermore, low acuity patients can be treated in a separate area such as a Clinical Decision Unit (CDU) to further reduce traffic in the ED. This method has been adopted by several healthcare organizations under different names including the Fast Track method or the split-flow model.


In 2004, John Muir Medical Centre in California opened a temporary CDU for a three-year period in place of a permanent CDU being built. It was a 7-bed mobile surgical unit set up in the hospital parking lot where non-emergent patients were monitored and treated. The temporary CDU reduced ED hold times, improved patient flow, increased the capacity of available inpatient beds, and eliminated the need to divert ambulances from coming to the ED at busy times. More about the use of CDUs to improve ED efficiency can be found in these resources:

Keeping Patients Vertical

One additional proven technique to reduce ED overcrowding is to keep patients vertical. Often times, EDs do not have enough beds to treat incoming patients. The idea is to keep non-emergent patients from unnecessarily occupying bed space if they can be treated in another manner. For example, allocating a patient lab test waiting area with chairs and recliners instead of having patients wait for their test results from beds. Another method is to opt for oral medication over intravenous (IV) injections wherever possible to keep low acuity patients upright, occupying less space. More information and ways to keep patients vertical in the ED:

Lean Process and Tools

Lean processes and tools can be used to predict trends, identify non-value-added steps and eliminate waste in any work flow. When lean techniques were applied to the ED setting in Florida Hospital, Orlando, the organization saw a decrease in LOS, and increases in patient visits per month, the percentage of patients highly ranking the overall ED care and admissions per month. They also saved $5.3 million after two years of implementation. The case study below describes the hospital’s lean ED care model and the results achieved through its implementation. Value stream mapping is a useful lean process tool that can be used to examine inefficiencies in existing ED work flows.

Key Takeaways

There are a number of demonstrated strategies for addressing the issue of ED overcrowding and associated long wait times. A number of innovative process improvements can be utilized to improve care and satisfaction of ED patients. Standardization of processes, use of evidence-based care protocols and making the best use of available space are key to ED improvements. Working in partnership with inpatient areas of the hospital to improve flow as well as identifying community-based resources to care for non-urgent patients are also possible strategies. 

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