<p>Dynamic Message Signs (DMS) — those big electronic boards over highways — display real-time traveler information: incident warnings, travel times, amber alerts, construction notices.</p> <p>Road511 captures the current message from every DMS sign across 30+ US states and Canadian provinces. Nobody else aggregates this data.</p> <h2> What You Get </h2> <div class="highlight js-code-highlight"> <pre class="highlight shell"><code>curl <span class="s2">"https://api.road511.com/api/v1/features?type=signs&amp;jurisdiction=GA&amp;limit=10"</span> <span class="se">\</span> <span class="nt">-H</span> <span class="s2">"X-API-Key: your_key"</span> </code></pre> </div> <div class="highlight js-code-highlight"> <pre class="highlight json"><code><span class="p">{</span><span class="w"> </span><span class="nl">"data"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="nl">"id"</span><span class="p">:</span><span class="w"> </span><span class="s2">"ga-sign-i85-042"</span><span class="p">,</span><span class="w"> </span><span class="nl">"jurisdiction"</span><span class="p">:</span><span class="w"> </span><span class="s2">"GA"</span><span class="p">,</span><span class="w"> </span><span class="nl">"name"</span><span class="p">:</span><span class="w"> </span><span class="s2">"I-85 NB at Clairmont Rd"</span><span class="p">,</span><span class="w"> </span><span class="nl">"latitude"</span><span class="p">:</span><span class="w"> </span><span class="mf">33.8103</span><span class="p">,</span><span class="w"> </span><span class="nl">"longitude"</span><span class="p">:</span><span class="w"> </span><span class="mf">-84.3179</span><span class="p">,</span><span class="w"> </span><span class="nl">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="nl">"message"</span><span class="p">:</span><span class="w"> </span><span class="s2">"CRASH AHEAD / I-85 NB AT SR 42 / RIGHT LANE BLOCKED"</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="p">]</span><span class="w"> </span><span class="p">}</span><span class="w"> </span></code></pre> </div> <p>The <code>message</code> field contains the exact text currently displayed on the sign, including line breaks encoded as <code>/</code>.</p> <h2> Why This Matters </h2> <p>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:</p> <ul> <li> <strong>Faster incident detection</strong> — sign changes before event feeds update</li> <li> <strong>DOT response time analysis</strong> — how long after an incident before a sign is posted</li> <li> <strong>Traveler information coverage</strong> — which corridors have DMS signs, which are blind spots</li> <li> <strong>Historical message patterns</strong> — Road511 now tracks message changes over time</li> </ul> <h2> Message History </h2> <p>Road511 records every message change in the <code>sign_message_history</code> table. Only actual changes are stored (not every poll), so you get a clean timeline of what each sign displayed and when.</p> <p>This is data that doesn't exist anywhere else publicly. No state DOT publishes a historical archive of DMS messages.</p> <h2> Use Cases </h2> <ul> <li> <strong>Navigation apps</strong> — show upcoming sign messages on the route</li> <li> <strong>Traffic management</strong> — monitor DMS coverage and response times</li> <li> <strong>Research</strong> — analyze traveler information effectiveness</li> <li> <strong>Emergency alerting</strong> — detect amber/silver alerts from sign text</li> </ul> <h2> Try It </h2> <ul> <li> <a href="https://map.road511.com" rel="noopener noreferrer">Live map</a> — click any sign marker to see current message</li> <li><a href="https://docs.road511.com" rel="noopener noreferrer">API docs</a></li> <li><a href="https://portal.road511.com" rel="noopener noreferrer">Free API key</a></li> </ul>