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GlossaryResponse performance and resources

Travel time

Understand emergency-service travel time, the timestamps behind it, and its difference from the full wait for help.

Travel time is the time a responding unit spends going to an incident, usually measured from its en-route timestamp to its recorded arrival. In an emergency-service report, the term should always be read with the source's exact endpoints: some agencies use a broader dispatch-to-arrival interval under the same label.

Washington's fire-service statute calls the interval after turnout, while units are en route until arrival, “response time.” San Francisco's police calls documentation instead labels dispatch-to-first-arrival “travel time.” Both are useful local definitions, but the numbers cannot be compared as though the clocks necessarily start at the same event. Washington RCW 35.103.020; San Francisco dataset explainer, revised September 2021

What the interval can show

Travel time helps describe how long it takes an assigned resource to reach a scene from its actual starting location. It is relevant to station placement, deployment, road access, and coverage. It does not by itself explain why a particular journey took longer. A record of elapsed time is not a record of traffic conditions, route choices, weather, or the crew's decisions.

The starting location may be a station, another incident, a hospital, or a temporary coverage position. A map showing the nearest station therefore does not establish where the responding unit began. Similarly, straight-line distance cannot reproduce a road journey with bridges, divided highways, or limited access points.

Travel should be distinguished from the earlier stages of answering, processing, and dispatching a call, and from getting a crew ready to move. It should also be distinguished from the time between arrival at an address and actual contact with a person needing assistance.

Example

Hypothetical: An ambulance is assigned at 14:10:00, marks en route at 14:11:00, and records arrival at 14:18:30. En-route-to-arrival travel is 7 minutes 30 seconds. Dispatch-to-arrival is 8 minutes 30 seconds.

If a dashboard uses the latter definition, its value includes the minute before movement. A reader should not subtract a separately published average turnout time from that incident's value: an average from a group of calls is not the actual turnout for this ambulance.

Now suppose a fire engine arrives at 14:16:00. A measure of first-unit arrival could show a shorter interval than ambulance arrival. Neither number is inherently wrong. They answer different questions about which resource reached the scene.

Common confusion

Travel time is not the complete response time experienced by a caller. It usually leaves out the period before the assigned unit starts moving. Nor does arrival automatically mean treatment began, the fire was controlled, or every required resource was present.

A modeled drive time is also different from a recorded travel time. A planning map may estimate journeys under specified assumptions; operational records describe individual responses through recorded status changes. A map's five-minute zone is not evidence that every actual call in that zone received a unit within five minutes.

A shorter travel time alone is not a complete quality judgment. Comparisons need incident urgency, resource type, geography, and the broader service outcome.

Checking the local measure

Identify the start event, arrival event, selected unit, and eligible calls before using a figure. Check whether canceled responses, missing timestamps, or implausible intervals were excluded. A blank arrival time should not become a zero-minute journey.

For trends, preserve the same definitions across years. A change from dispatch-based to en-route-based timing could make reported travel look faster even without any change in driving. Explain such a change alongside the chart rather than presenting it as an operational improvement.

Sources