What Is a Sig Alert and How Does the CHP Define Traffic Delays?

* **Unplanned Event:** The delay must be caused by an unscheduled incident, such as a collision, vehicle fire, or hazardous spill. Scheduled roadwork does not trigger a Sig Alert. * **Lane Blockage:** The incident must block at least one travel lane on a freeway or state highway. * **Duration:** CHP dispatchers must estimate that the lane blockage and resulting delay will last for at least 30 minutes. Once these conditions are met, the CHP issues the alert to local media, traffic reporting services, and digital highway signs. When the lanes reopen and traffic begins to recover, the CHP officially cancels the alert. ## The Origin of the Sig Alert The term "Sig Alert" is unique to California. It is named after Loyd Sigmon, a co-owner and engineer at the Los Angeles radio station KMPC.

In the mid-1950s, Sigmon developed a receiver that could pick up CHP radio broadcasts. He proposed a system where the CHP could transmit alerts about major emergencies or traffic hazards directly to radio stations, which would then broadcast the warnings to the public. The system was adopted in 1955 and eventually became dedicated exclusively to major traffic disruptions, with the name shortened to "Sig Alert." ## Where to Find Active Sig Alerts Drivers can access real-time information regarding active Sig Alerts and highway conditions through several official platforms: * **CHP Traffic Incident Information Page:** The official CHP dispatch website provides public access to live incident logs, showing active lane closures and traffic hazards. * **Caltrans QuickMap:** Managed by the California Department of Transportation, this website and mobile app display real-time traffic speeds and active alerts on an interactive map. * **Changeable Message Signs:** Electronic signs positioned above California freeways display real-time warnings to drivers approaching an active incident.

## How Sig Alerts Help Manage Traffic Sig Alerts serve a critical role in traffic management and public safety. By providing early warnings, the CHP aims to: * **Prevent Secondary Collisions:** Warning drivers to slow down before they reach the back of a traffic queue reduces rear-end collisions. * **Reduce Congestion:** Informing motorists of a delay allows them to take alternate routes, reducing the volume of vehicles entering the bottleneck. * **Facilitate Emergency Response:** Fewer vehicles in the backup makes it easier for emergency vehicles and tow trucks to reach the scene and clear the incident.