Building a Modern 911 Dispatch and Mass Notification System: A Comprehensive System Design Guide
Published: (December 9, 2025 at 10:55 AM EST)
4 min read
Source: Dev.to
Source: Dev.to
Introduction
Designing a 911 dispatch and mass notification system is one of the most critical challenges in public safety technology. Lives depend on sub‑second response times, accurate location data, and reliable communication across multiple channels. This guide explores the architecture, technologies, and best practices for building a modern emergency dispatch system that can handle the demands of contemporary emergency response.
Unlike traditional notification systems, a 911 dispatch platform must integrate real‑time mapping, unit tracking, critical infrastructure monitoring, and multi‑agency coordination while maintaining absolute reliability.
Core Dispatch Capabilities
- Real‑time incident creation and management
- Automatic location detection and geocoding
- Multi‑agency unit dispatch and coordination
- Live unit tracking and status updates
- Incident priority classification (life‑threatening, urgent, routine)
- CAD (Computer‑Aided Dispatch) integration
- Audio recording and logging of all communications
Mass Notification Features
- Emergency alerts to citizens (tornado warnings, AMBER alerts, evacuation orders)
- Multi‑channel delivery (SMS, voice calls, push notifications, sirens, digital signage)
- Geographic targeting (polygon zones, radius‑based, administrative boundaries)
- Template management for common alert types
- Multi‑language support
- Accessibility compliance (text‑to‑speech, hearing‑impaired alerts)
Mapping & Location Intelligence
- Real‑time interactive mapping with sub‑second updates
- Automatic vehicle location (AVL) for all units
- Route optimization and turn‑by‑turn navigation
- Geofencing for jurisdictional boundaries
- Point‑of‑interest databases (hospitals, schools, fire hydrants)
- Building floor plans and pre‑incident planning data
- Traffic layer integration
- Weather overlay
Integration Requirements
- E911/NG911 systems for automatic caller location
- RMS (Records Management System)
- Fire/EMS patient‑care reporting
- Body‑camera and dash‑camera systems
- NCIC/NLETS for warrant checks
- Hospital bed availability systems
- Mutual‑aid coordination with neighboring agencies
Performance
- P99 incident creation time: < 500 ms
- Map refresh rate: 1–2 seconds for unit positions
- Mass notification delivery: 10,000 messages/second
- Support for: 500+ concurrent dispatchers
- Handle: 100,000+ incidents per day
Reliability
- 99.999 % uptime (Five Nines – less than 5.26 minutes downtime/year)
- Redundant infrastructure across multiple data centers
- Automatic failover in < 5 seconds
- Zero data loss guarantee
- Disaster recovery with RPO < 1 minute
Security & Compliance
- CJIS (Criminal Justice Information Services) compliance
- HIPAA compliance for medical data
- End‑to‑end encryption for all communications
- Role‑based access control (RBAC)
- Comprehensive audit logging
- SOC 2 Type II certification
Latency Requirements
- Caller‑to‑dispatcher connection: < 2 seconds
- Dispatch‑to‑unit notification: < 3 seconds
- GPS position update: 1–5 second intervals
- Mass alert delivery: < 10 seconds for critical alerts
System Architecture Overview
┌─────────────────────────────────────────────────────────────────┐
│ CLIENT LAYER │
├─────────────┬──────────────┬──────────────┬────────────────────┤
│ Dispatcher │ Mobile │ Citizen │ Admin │
│ Console │ Units │ Alert App │ Dashboard │
│ (Web) │ (iOS/And.) │ (Mobile) │ (Web) │
└──────┬──────┴──────┬───────┴──────┬───────┴─────┬──────────────┘
│ │ │ │
└─────────────┴──────────────┴─────────────┘
│
▼
┌─────────────────────────────────────────────┐
│ API GATEWAY + LOAD BALANCER │
│ (Kong/AWS ALB with Auto‑scaling) │
└──────────────────┬──────────────────────────┘
│
┌──────────────────┴───────────────────┐
│ │
▼ ▼
┌──────────────────┐ ┌──────────────────┐
│ CAD/DISPATCH │ │ NOTIFICATION │
│ SERVICE │ │ SERVICE │
│ │ │ │
│ - Incident Mgmt │ │ - Alert Creation │
│ - Unit Dispatch │ │ - Multi‑channel │
│ - Status Updates │ │ - Targeting │
└────────┬─────────┘ └─────────┬────────┘
│ │
└──────────────┬──────────────────────┘
│
▼
┌─────────────────┐
│ EVENT STREAM │
│ (Kafka/AWS │
│ Kinesis) │
└────────┬────────┘
│
┌───────────────┼───────────────┐
│ │ │
▼ ▼ ▼
┌────────────┐ ┌────────────┐ ┌────────────┐
│ MAPPING │ │ LOCATION │ │ WORKER │
│ SERVICE │ │ TRACKING │ │ POOL │
│ │ │ SERVICE │ │ │
│ - Real‑time│ │ - GPS │ │ - Message │
│ layers │ │ - AVL │ │ Delivery │
│ - Routing │ │ - Geofence │ │ - Retries │
│ - Geocode │ │ │ │ - Status │
└────────────┘ └────────────┘ └────────────┘
│ │ │
└───────────────┼───────────────┘
│
┌───────────────┴───────────────┐
│ │
▼ ▼
┌─────────────────┐ ┌─────────────────┐
│ DATABASES │ │ EXTERNAL │
│ │ │ SERVICES │
│ - PostgreSQL │ │ - Twilio (SMS) │
│ - TimescaleDB │ │ - SendGrid │
│ - MongoDB │ │ - FCM/APNS │
│ - Redis Cache │ │ - Mapbox/Esri │
│ │ │ - Google Maps │
│ │ │ - Weather API │
└─────────────────┘ └─────────────────┘Mapping Providers
1. Esri ArcGIS for Public Safety
- Industry standard for 911/dispatch systems
- Real‑time GIS capabilities with ArcGIS GeoEvent Server
- Advanced spatial analysis and geocoding
- Pre‑built public safety data models
- Offline capability for disaster scenarios
- 3D visualization for multi‑story buildings
2. Mapbox
- Highly customizable vector maps
- Superior performance for real‑time tracking
- Navigation SDK for turn‑by‑turn routing
- GL JS for smooth web animations
- Cost‑effective for high‑volume usage
3. Google Maps Platform (Emergency Services)
- Specialized Emergency Location Service (ELS)
- Accurate indoor positioning
- Real‑time traffic data
- Street View integration for pre‑incident planning
- Places API for POI data
Real‑time GPS Position Update Flow
{
"unitId": "ENGINE-401",
"position": {
"lat": 41.8781,
"lng": -87.6298,
"accuracy": 5,
"heading": 175,
"speed": 35
},
"timestamp": "2024-12-09T14:23:45.123Z",
"status": "ENROUTE",
"incidentId": "INC-2024-123456",
"eta": 180 // seconds
}Key Features to Implement
- Geofencing: Automatic status updates when units enter/leave zones
- Breadcrumb Trails: Historical path tracking for post‑incident review
- Dead Reckoning: Position estimation during GPS signal loss
- Automatic Vehicle Location (AVL): Integration with vehicle telematics
- Indoor Positioning: Bluetooth beacons or Wi‑Fi triangulation for buildings
Best Practices for Accurate Address Matching
- Use multiple geocoding providers with fallback (Esri → Google → Mapbox)
- Maintain a local address database with corrections
- Handle common address variants (“Street” vs “St”)
- Support intersection geocoding (“Main St & Elm Ave”)
- Apply fuzzy matching for misspelled addresses
- Integrate what3words for precise location in rural areas