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How to explain UHU from UFOs to your city manager

EMS unit hour utilization is always calculated as the number of transports divided by the total number of unit hours in the measurement interval

“My City Manager doesn’t know UHU from UFOs. Is there an easy way to explain it?”

Chances are you’re dealing with someone who’s not intimately familiar with the operations of an EMS system, so before you get into the details of what UHU is, explain why it exists in the first place — to have a standardized, shorthand way to measure workload levels in your system and to allow comparison to other systems.

UHU, or unit hour utilization, itself is fairly straightforward. Unit Hour Utilization (UHU) is calculated by dividing the number of EMS transports by the number of “unit hours,” with one unit hour defined as a fully equipped and staffed vehicle in your EMS system. If your system has 10 ambulances around the clock, there are 240 unit hours in a 24-hour period. If those 10 ambulances do 120 transports in 24 hours, you would calculate your system’s UHU as follows:

120 transports/240 unit hours = .5 UHU

Of course, many systems vary staffing levels to meet demand, and UHU is typically measured over longer intervals than 24 hours — but UHU in EMS is still calculated as the number of transports divided by the total number of unit hours in the measurement interval.

The higher the ratio, the more productive the system, in the sense that you’re getting more transports out of fewer ambulances. Measuring UHU also helps an EMS system match the number of on-duty units [supply] that are required to achieve response times [demand].

If your city manager’s eyes are glazed over at this point, a comparison to something familiar might be useful. For example, if your local UPS service uses 10 trucks to deliver 100 packages in an hour, it would less productive than a FedEx service that uses 5 trucks to deliver the same number of packages in the same hour, all things being equal.

Variables that impact EMS UHU

To fully benefit from using the UHU benchmark, there are a number of modifiers that must be considered. Each of the following could skew a system’s UHU:

Population and call density: For example, an urban community with short transport distances will have a significantly different UHU than suburban or rural services.

Geography: Road condition and layout, traffic congestion, bridges and other factors can affect the comparison value of UHU. An EMS system in a city where roads are well laid-out and traffic flows freely will likely experience higher UHU than a similar EMS system in a city with decaying infrastructure, inefficient routes and traffic congestion.

Time-on-Task: This measurement, the time it takes to completely manage each incident, varies and has to be considered to have an accurate UHU. For example, if crews cannot quickly offload patients at receiving hospitals because of bed availability, paperwork or other issues, time-on-task increases.

Scheduling: Shift patterns and crew scheduling practices can also influence a system’s UHU. Typically, shorter shifts can tolerate higher UHU than 24-hour shifts, where high usage coupled with little opportunity for rest could increase risk.

The goal is to fully balance and optimize these variables along with clinical factors, response times, employee satisfaction and fiscal realities.

Accurately measuring UHU helps EMS leaders demonstrate that their systems are providing the community exceptional value — or defend their budget if need be. If your city manager or other stakeholders don’t understand UHU, you’re missing an important opportunity to make your case for additional budget for staffing, ambulances or stations.

For more than three decades, the Fitch & Associates team of consultants has provided customized solutions to the complex challenges faced by public safety organizations of all types and sizes. From system design and competitive procurements to technology upgrades and comprehensive consulting services, Fitch & Associates helps communities ensure their emergency services are both effective and sustainable. For ideas to help your agency improve performance in the face of rising costs, call 888-431-2600 or visit