Unit Hour Utilization
Unit utilization is a factor in determining whether there is an appropriate emergency services system response. For purposes of this analysis, unit utilization is calculated by taking the total hours the unit is committed to incidents for the year divided by the total hours in a year. Expressed as a percentage, it identifies the amount of time the unit is committed but more importantly the amount of time the unit is available. In 2016, Henrico County, Virginia conducted a study of unit utilization. Through their study they developed a scale to identify the community impact on travel time and availability of their emergency medical units. 1 The following table illustrates how unit utilization impacts the system reliability.
Factor
Indicator
Description
Personnel can maintain training requirements and physical fitness and can consistently achieve response time benchmarks. Units are available to the community more than 75 percent of the day. Units below 0.16 should be evaluated for more efficient use as additional operating capacity is available. Community availability and unit sustainability are not questioned. First-due units are responding to their assigned community 75 percent of the time, and response benchmarks are rarely missed. At this level, agency leaders must understand that commitment factor increases are imminent. The community this unit serves will begin to see increasingly longer response times as neighboring stations send apparatus during one out of four calls. In this range, the community served will experience delayed incident responses. Just under 30 percent of the day, first-due ambulances are unavailable; thus, neighboring responders will likely exceed goals. Agency leadership should immediately begin identifying funding sources to provide relief. At this range, commitment factors are only expected to increase. Not Sustainable: Commitment Threshold – shows our community has less than a 70 percent chance of timely emergency service and immediate relief is vital. Personnel assigned to units at or exceeding 0.3 may show signs of fatigue and burnout and may be at increased risk of errors. Required training and physical fitness sessions are not consistently completed.
Ideal Commitment Range
16%to24%
25%
System Stress
26% to 29% Evaluation Range
30%or more
Line in the Sand
As illustrated above, when utilization is below 25% the system is operating well. At 25% utilization there is stress on the system due to the reduced reliability of a first responding unit responding from the service area of the emergency. When utilization is between 25% and 30% it is time to evaluate the need for additional emergency response resources and at 30% or more the system is not sustainable and additional units should be added to reduce system strain.
1 https://www.fireengineering.com/apparatus-equipment/how-busy-is-busy/#gref
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