The California Healthcare Foundation has underwritten a study looking at ambulance diversions across the state. Findings in this phase 1 report showed that state wide emergency departments (EDs) were on divert an average of 10% in 2005. Emergency department closings to ambulances continue to confound hospital administrators. You can read about a recent survey showing patient flow as an increasing problem here.

ED diversions also frustrate policy wonks and consultants due to the almost total absence of public reporting. Certainly hospitals (and their state associations), emergency response districts, along with some local and state governments, know their emergency room diversion statistics - they just aren't publicly available. Even though access to data is improving, organizations like the CHF have to pay to collect much of their data.

ED diversion affects patient care resources and may result in
continuity of care issues, such as the patient's physician not having
hospital privileges at the alternate receiving hospital and the
hospital not having the patient’s medical records. Diversion also
results in longer hours for ambulance units and, when patients cannot
be transported to hospitals within their health plans, greater overall
health care costs.

This study is part of a project to measure and publicly report the
extent of ambulance diversion. It identifies practices that can help
those communities that have had difficulty resolving their diversion

As expected, the study finds that ED diversions occur mostly in urban areas. Increasingly districts and hospitals are implementing "no diversion" policies - in other words they simply take the patients that they used to refuse - even though in most cases little or nothing has been done to improve emergency department overcrowding or patient flow.

You can download your version of the first report here.