Unit available time

Unit available time is the recorded point when a response resource becomes available for another assignment under the agency's status rules. It describes readiness for dispatch. It does not necessarily mean the resource has returned to its station or home location, and it should be distinguished from earlier completion milestones.

Availability is a recorded status

A useful dataset identifies how availability is entered and what the status means locally. The timestamp may be part of a dispatch record, an EMS record, or another operational system.

NEMSIS version 3.5.1 defines a back-in-service field that includes availability for response and explicitly does not require return to the home location. It also contains separate fields for home-location return and call completion. NEMSIS time dictionary.

Example

Hypothetical: An ambulance completes a patient handoff at 18:10, is recorded back in service at 18:20, and reaches its assigned home location at 18:35. Under the stated source definition, it becomes available at 18:20.

Using the home-location timestamp would add 15 minutes to a measure of time until availability. Using the handoff timestamp would omit ten minutes. The correct endpoint depends on the question, so all three events should keep distinct labels.

Common confusion

Available does not mean idle for the rest of the shift. A unit can receive another assignment soon afterward. A snapshot showing availability at one moment cannot establish how much of the day was uncommitted.

A unit's available timestamp also differs from the number of units available across the system. That count requires the status of multiple resources at the same point in time.

Scene departure and assignment clearance can be related to availability, but the terms are not universally interchangeable. A local dictionary may equate particular fields; that equivalence must be documented before combining them.

Measuring time committed

For an assignment-duration measure, use a defined start and the appropriate available endpoint for the same unit. Check for overlaps, missing status changes, and impossible sequences before adding durations.

Explain which activities the method includes. A total based on dispatch-to-availability differs from scene time or transport time. When publishing a percentage of staffed hours committed to calls, use compatible resource-hour totals in both numerator and denominator. A count of availability events alone cannot supply those hours.

Related terms

• Unit clear time
• Unit status
• Hospital turnaround time
• Unit-hour

Sources

• NEMSIS: Version 3.5.1 eTimes Schema Documentation — eTimes.13, .15, and .16 distinguish back in service, home-location return, and completion of call tasks.