On Thursday morning, Los Angeles news radio station KNX aired a call from a ten-year-old girl who wanted to know the answer to a question that comes up from time to time: what is a SigAlert?

L.A. drivers hear about SigAlerts almost every day. They are issued after car accidents, fires, water main breaks, landslides, and other disruptions.

So what are they? And where did the term come from?

A SigAlert is a notification system used by the California Highway Patrol to alert drivers about incidents that disrupt traffic flow, typically on interstates or major roads.

Whenever a freeway is closed due to a crash – that’s a SigAlert.

While many Californians might assume “Sig” is short for “Signal,” it’s not. “Sig” was a person.

Loyd “Sig” Sigmon was the chief engineer for radio station KMPC in Los Angeles. In 1955, he devised a plan to boost ratings by asking Los Angeles police to call him whenever there was a major crash.

Police weren’t initially on board, so Sigmon instead developed a machine that tapped into LAPD’s radio dispatch center to record and playback crash advisories on the air, as documented by The Los Angeles Times.

Understanding the inherent public safety benefits, LAPD’s chief approved of the concept, and Sigmon made his alert system available to every radio station that wanted it.

The very first SigAlert was broadcast by six radio stations on Labor Day 1955 after train derailment and ironically, it ended up causing its own traffic jam.

Within three months, 86 SigAlerts were issued by Los Angeles police, and the rest -as they say- is history.