A Short History of Computer-Aided Dispatch in Seattle
Published May 9, 2026 · 10 minute read
The data on the Seattle Breaking live map is generated by a Computer-Aided Dispatch (CAD) system — software that helps emergency dispatchers route calls to available units in real time. CAD seems like an unremarkable piece of plumbing today, but the path from paper run-cards to the unified regional CAD platform that Seattle Fire and SPD use now spans about fifty years and involves a surprising number of political fights, vendor disputes, and procurement decisions that shaped which units arrive at your door today. This article is a brief tour of that history.
The pre-CAD era: paper, magnetic boards, and grease pencils
Through the 1960s and into the early 1970s, Seattle Fire and Seattle Police both operated dispatch centers that ran on paper. A 911 call (or, before 1968, a call to a seven-digit emergency number) was answered by a call-taker who scribbled the address and complaint onto a run-card and handed it physically to a dispatcher. The dispatcher kept a mental or paper-based map of which units were in service and which were on calls, and decided who to send. The work demanded extraordinary memory and routing intuition from senior dispatchers, who often had decades of experience and knew the city block by block.
Tracking the status of units was done on a magnetic status board — a metal panel with magnetic strips for each unit, labeled with each unit's call sign and color-coded by status. Available units were in one column. Dispatched units were moved into the column for their call. On-scene units were moved again. Status updates happened by hand, in real time, by dispatchers who never sat down during their shifts.
This system worked surprisingly well. It also occasionally broke spectacularly. Misplaced run-cards. Forgotten move-ups. Units sent to addresses across town from where they were needed. The pressure for automation was visible by the late 1960s, but the technology wasn't ready.
The 1970s: mainframe-era CAD
Seattle was an early adopter of computer-aided dispatch by national standards. The first CAD system at Seattle Fire went into limited operation in the mid-1970s, running on a city-owned mainframe and accessed by dispatchers through CRT terminals. The system maintained a database of streets and addresses, tracked unit status, generated incident numbers, and produced printed dispatch tickets. It did not, in its earliest version, do automatic recommendation of which units to send — that was still a human decision — but it removed the paper handling and the magnetic status board.
SPD adopted a separate CAD system around the same time, also mainframe-based, also CRT-terminal-accessed, and also independently chosen and configured. The decision to keep the two systems separate was partly technical (the two agencies' workflows are different) and partly political (each department wanted control of its own tools). The decision had consequences that lasted into the present — Seattle has spent five decades occasionally trying, and never quite succeeding, to unify fire and police CAD onto a single platform.
The 1980s and 1990s: AVL, mobile data, and routing engines
The two innovations that distinguish modern CAD from 1970s CAD are automatic vehicle location (AVL) and routing engines. AVL — the ability to know in real time where every unit physically is, via GPS or its predecessors — arrived in fire apparatus and police vehicles in stages through the 1980s and 1990s. Early systems used commercial radio triangulation; GPS-based AVL became practical by the late 1990s and standard by the early 2000s.
Once dispatch knew where units actually were, the routing engine could replace the dispatcher's intuition about who was closest with an actual computed answer. Modern CAD recommends a response plan and a specific set of units, and the dispatcher accepts or modifies that recommendation. The dispatcher's role shifted from "who do I send" to "the system recommends X, do I have any reason to override that." For a typical call, the answer is no, and the routing recommendation is what gets dispatched.
Mobile data terminals — screens in the front of the apparatus that receive dispatch information directly — arrived in Seattle apparatus in the late 1990s and early 2000s. Before MDTs, dispatch was voice-only over radio. After MDTs, the unit got a printed-or-screen ticket with the address, the call type, the building access details, and any prior-call history at that location. This shifted some workload off the radio (which is a scarce resource) and produced richer dispatch records as a side effect.
The 2000s: the unification attempts
Around 2003, the City of Seattle launched a project to unify fire and police CAD onto a single vendor platform. The reasoning was straightforward — shared dispatch data, better mutual-aid coordination, lower licensing costs, a single training pipeline for dispatchers. The execution was harder. Fire and police dispatch workflows are different at a fundamental level (fire calls are about apparatus and stations, police calls are about districts and individual officers), and the candidate vendors all had stronger products on one side or the other.
The unification effort, after years of work, did not produce a unified product. SFD continued on one vendor's platform, SPD on another. The two systems were eventually integrated at a data-exchange level — they could send incidents to each other for cross-agency response — but they remained separate products with separate interfaces, separate databases, and separate update cycles. This is the state of affairs that persists today.
The 2010s: regionalization and PSERN
The defining infrastructural project of the 2010s for Puget Sound public safety was the Puget Sound Emergency Radio Network (PSERN), a regional voter-approved replacement of the aging analog and partially digital radio infrastructure across King County. PSERN brought Seattle, Bellevue, King County Sheriff, and dozens of smaller agencies onto a single P25 trunked digital radio system, completed in stages between roughly 2018 and 2022.
PSERN matters for CAD because radio infrastructure and dispatch software are tightly coupled. A unified radio system makes cross-agency dispatch much cleaner — a Bellevue engine responding to a Seattle call is on the same radio network as Seattle's own units, with no patch or interoperability gateway required. Mutual-aid responses, automatic-aid agreements, and major-incident command structures all became more efficient as PSERN came online.
Around the same time, both SFD and SPD upgraded their CAD platforms. The current generation of CAD software runs on commodity servers rather than mainframes, includes richer GIS integration, supports text-from-911 (Next-Generation 911), and exposes a documented data export pipeline. The export pipeline is what produces the Seattle Real Time Fire 911 dataset and the SPD Call Data dataset that this site uses.
The 2020s: open data and encryption
Two trends define the current decade. One is the maturing of the open-data publication pipeline. The Seattle Open Data portal, launched around 2010, has continuously expanded the public-safety datasets it publishes. Today it includes near-real-time fire dispatch data, somewhat-delayed police call data, monthly summaries, historical archives, and a growing set of supporting reference datasets (station locations, response zones, apparatus rosters). Civic tech projects — including this site — depend on those publications.
The other trend is encryption. As discussed in our scanner-listening article, SPD encrypted its operational radio traffic in 2021. The encryption decision was specifically about radio audio, not CAD data — the open-data exports continued — but the move pulled a longstanding source of independent verification (scanner listeners) off the table. The relationship between public dispatch data and public radio traffic is now asymmetric: anyone can read SPD's clearance data after the fact, but no one outside SPD can hear what is happening in real time.
What this means for the live feed
Three concrete consequences for what you see on Seattle Breaking:
- Fire data is fresher than police data. This is partly a CAD architecture choice (the SFD platform exports at dispatch; SPD exports at clearance) and partly a policy choice (SPD reviews records before export). The five-decade history of separate platforms is why these two feeds behave differently.
- The data is rich because the CAD systems are rich. Each incident has a precise timestamp, a structured type code, a geocoded location, and an apparatus list — because modern CAD captures all of that in the course of routine operation. The dataset is not generated by a separate transparency process; it falls out of the operational system as a side effect of dispatching.
- Future regionalization could expand the dataset. If, at some future point, a regional CAD platform unified Seattle, Bellevue, and King County dispatch, the export feed could expand to include cross-agency incidents in a single stream. That would change what a live regional feed could look like. There is no such project announced today, but the infrastructure built for PSERN is most of the way there.
The data we surface today reflects fifty years of incremental infrastructure decisions, several of them controversial at the time. The history is mostly invisible to a reader looking at a map of dispatch pins, but it shapes what is on that map and what is not.