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Dispatch time

Dispatch time can mean a recorded clock time or an interval before assignment. Learn how to identify the field and avoid comparing different measures.

Dispatch time can mean either the recorded moment when a resource is assigned or notified, or an elapsed interval leading to that event. The source must say which meaning applies. A clock value such as 09:14 and a duration such as 90 seconds describe different kinds of information.

Timestamp or duration

A timestamp locates an event on a timeline. A duration measures the difference between two events. A column titled “dispatch time” is ambiguous until its data dictionary identifies the event or the pair of endpoints.

The NEMSIS version 3.5.1 time dictionary separately identifies when dispatch is notified and when the responding unit is notified. Those are distinct fields, even when they happen close together. NEMSIS time-field definitions.

Example

Hypothetical: A source records a request at 09:12:30 and unit notification at 09:14:00. Its dispatch timestamp is 09:14:00. A locally defined request-to-notification interval is 90 seconds.

If another source starts its interval at 09:13:00, when a separate dispatch center received the request, that interval is 60 seconds. The shorter result does not prove the second process was faster. The clocks begin at different events, so the methods must be reconciled before comparison.

Common confusion

Unit notification is not necessarily the moment the vehicle begins moving. Turnout or preparation can occur between those events. Treating a dispatch timestamp as an en-route timestamp can move that preparation time into the apparent travel interval.

Dispatch time also does not identify the first arrival or the final incident outcome. It marks an earlier stage, and a dispatched unit can later be canceled before arriving.

Working with the field

Use the full date, time, and applicable time zone when calculating durations. A clock time alone can produce errors for events crossing midnight. Keep missing values separate from midnight values; they are not interchangeable.

When publishing, prefer a label that names the interval, such as “call received to unit notified.” Explain whether the timestamp belongs to the first unit, a specific unit, or an incident-level summary. A multiunit event can have several dispatch times, and collapsing them into one requires an explicit rule.

Sources