Dynamic Message Signs (DMS) — those big electronic boards over highways — display real-time traveler information: incident warnings, travel times, amber alerts, construction notices.
Road511 captures the current message from every DMS sign across 30+ US states and Canadian provinces. Nobody else aggregates this data.
What You Get
curl "https://api.road511.com/api/v1/features?type=signs&jurisdiction=GA&limit=10" \
-H "X-API-Key: your_key"
{"data":[{"id":"ga-sign-i85-042","jurisdiction":"GA","name":"I-85 NB at Clairmont Rd","latitude":33.8103,"longitude":-84.3179,"properties":{"message":"CRASH AHEAD / I-85 NB AT SR 42 / RIGHT LANE BLOCKED"}}]}The message field contains the exact text currently displayed on the sign, including line breaks encoded as /.
Why This Matters
DMS messages are a leading indicator. The sign updates within minutes of an incident, often before the event appears in some 511 feeds. Cross-referencing sign messages with traffic events gives you:
- Faster incident detection — sign changes before event feeds update
- DOT response time analysis — how long after an incident before a sign is posted
- Traveler information coverage — which corridors have DMS signs, which are blind spots
- Historical message patterns — Road511 now tracks message changes over time
Message History
Road511 records every message change in the sign_message_history table. Only actual changes are stored (not every poll), so you get a clean timeline of what each sign displayed and when.
This is data that doesn't exist anywhere else publicly. No state DOT publishes a historical archive of DMS messages.
Use Cases
- Navigation apps — show upcoming sign messages on the route
- Traffic management — monitor DMS coverage and response times
- Research — analyze traveler information effectiveness
- Emergency alerting — detect amber/silver alerts from sign text
Try It
- Live map — click any sign marker to see current message
- API docs
- Free API key