Response time

Response time is an elapsed interval between specified stages of a public-safety response. Its start might be call receipt, dispatch, or the beginning of travel; its end might be a first unit's arrival or another defined milestone. A response-time number is incomplete without those endpoints and the records included in its calculation.

The label can describe different intervals

A resident may think of response time as the whole wait from requesting help until responders arrive. An agency's operational measure may begin later. Both can be useful, but they answer different questions.

Washington's RCW 35.103.020 defines response time for that chapter as the interval after turnout, beginning when units are en route and ending at arrival. San Francisco's dispatch explainer describes separate measures beginning at call receipt or entry into the dispatch queue. These named examples show why the label cannot supply a universal formula. Washington definitions; San Francisco timestamp explanation.

Before comparing agencies, rewrite each measure in plain language: “call receipt to first arrival,” for example, or “unit begins traveling to unit arrival.” If those descriptions differ, the figures are not directly equivalent.

Example

Hypothetical example: A call is received at 12:00, a unit is notified at 12:01, the unit starts traveling at 12:02, and it arrives at 12:07.

The interval from notification to travel is one minute. Travel takes five minutes. Call receipt to arrival takes seven minutes. A measure beginning at notification would show six minutes instead.

Each calculation is correct for its chosen endpoints. Calling all four values “response time” without qualification would conceal what was measured. The example also omits any wait before the communication was answered, so it should not be described as the entire time from dialing for help.

Common confusion

Response time versus travel time: Travel covers movement from a defined starting milestone to arrival. A broader response measure can include processing, waiting for assignment, or turnout as well.

First arrival versus all resources arriving: The first arriving unit's interval can differ from the time required for a specified set of personnel and equipment to reach the scene. One does not establish the other.

Average versus percentile: An average summarizes the arithmetic mean. A 90th percentile describes a threshold reached by approximately nine tenths of included observations under a stated method. Identical units do not make those statistics interchangeable.

Define the eligible responses

A useful measure states the agency, period, service type, priority, and whether the unit of analysis is an incident or an individual responding unit. Multiple units on one incident can otherwise give a large response more weight than a small one.

It also explains canceled calls, missing timestamps, impossible time sequences, and responses that never reached the scene. Removing those records may be appropriate for a particular interval, but the exclusions should be visible.

Different call mixes can change an overall result. A month with more routine requests may not be comparable to a month dominated by urgent incidents unless the analysis accounts for those categories.

Reading performance claims

Compare the observed measure with a target only when the endpoints and eligible calls match. A target for travel cannot be evaluated using call receipt to arrival, or vice versa. There is no single response-time threshold established by this glossary.

For trends, preserve the timestamp definitions and software-change notes. A new automatic status update can change recorded intervals even if the underlying activity changes less. The number is most useful when its method is as transparent as its minutes and seconds.

Related terms

• Call-processing time
• Turnout time
• Travel time
• Total response time
• 90th percentile response time

Sources

• Washington State Legislature — RCW 35.103.020, checked November 2, 2026. Defines turnout and response for a particular statutory context.
• City and County of San Francisco — Law Enforcement Dispatched Calls for Service, revised September 10, 2021, time-interval sections. Provides distinct call-receipt and queue-entry measures and limitations of incident timestamps.