Introduction: Annual ambulance diversion hours in Boston increased more than six-fold from 1997 to 2006. Although interventions and best practices were implemented, there was no reduction in the number of diversion hours.

Objectives: A consortium of Boston teaching hospitals instituted a two-week moratorium on citywide diversion from 02 October 2006 to 15 October 2006. The hypothesis was that there would be no significant difference in measures of hospital and emergency medical services (EMS) efficiency compared with the two weeks immediately prior.

Methods: A total of nine hospitals and the municipal emergency medical services in Boston submitted data for analysis. The following mean daily hospital measures were studied: (1) emergency department volume; (2) number of emergency department admissions; (3) length of stay (LOS) for all patients; and (4) number of elopements. Mean EMS at-hospital time by destination and the percent of all Boston EMS transports to each hospital destination were calculated. The median differences (MD) were calculated as “before” minus “during” the study period and were compared with paired, Wilcoxon, non-parametric tests. Additional mean EMS measures for all destinations included: (1) to hospital time; (2) number of responses with transport initiated per day; (3) incident entry to arrival; and (4) at-hospital time.

Results: The LOS for admitted patients (MD = 0.30 hours; IQR 0.10,1.30; p = 0.03) and number of daily admissions (MD = -1.50 patients; IQR -1.50, -0.10; p = 0.04) were significantly different statistically. The results for LOS for all patients, LOS for discharged patients, ED volume, EMS time at hospital by destination, number of elopements, and percent of Boston EMS transports to each hospital revealed no statistically significant differences. The difference between the study and control periods for mean EMS to hospital time, at-hospital time, and incident entry to arrival was a maximum of 0.6 minutes. The vast majority of EMS respondents to an online survey believed that the “no diversion” policy should be made routine practice.

Conclusions: The LOS for admitted patients decreased by 18 minutes, and the number of admissions increased by 1.5 patients per day during the study period. The “no diversion” policy resulted in minimal changes in EMS efficiency and operations. Diversion was temporarily eliminated in a major city without significant detrimental changes in ED, hospital, or EMS efficiency.