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What is a SIGALERT?

Sigalert, I-405, Traffic

Sigalert on I-405 caught on traffic camera. Image from California Dept. of Transportation.

The term "Sig Alert" is so common that it is often used to describe any kind of congestion scenario. It is reported to be listed in the New Shorter Oxford English Dictionary Dictionary. The bumper car ride at Pacific Park on the Santa Monica Pier is named "Sig Alert EV."

By the 1950s, radio had become a key means of communicating emergency information to the public. Enter Loyd C. "Sig" Sigmon, who was a local Los Angeles radio executive for Gene Autry's Golden West Broadcasters. He was looking for ways to attract radio listeners and, considering L.A.'s rapidly growing motorized public, thought there would be interest in timely notices of traffic jams. However, the Los Angeles Police Department, then also responsible for traffic enforcement on L.A. freeways, said they could not give just one radio station special access to information and, at the same time, were too busy to call all radio stations every time there was a major traffic incident. Sigmon had served in the U.S. Army Signal Corps during the war, so he had some expertise with using and employing radio communications. He developed a specialized radio receiver/tape recorder device to which LAPD would just have to make one broadcast per bulletin. LAPD Chief William H. Parker agreed to work with Sigmon on his proposal, but, insisted that his receiver device must be available to all interested radio stations. Sigmon had hoped for a monopoly on traffic information, but agreed to see that his proposal was realized. Half a dozen radio stations initially arranged for installation of receivers. The first bulletin went out on January 22, 1956. Initially, LAPD bulletins trickled out about one per day. However, other police departments began sending in their bulletins. Public response was so positive that, Chief Parker, reported to be an initial skeptic, became a believer. The story goes that Chief Parker was the one to label the bulletins "Sigmon traffic alerts." The term was later shortened to "Sig Alerts."

On October 1, 1969, LAPD turned over responsibility for traffic enforcement on L.A. freeways to the California Highway Patrol. Soon afterward, CHP took over management of the Sig Alert system. The agency then expanded the Sig Alert system statewide. CHP currently defines a "Sig Alert" as any unplanned event that blocks more than one lane of traffic for thirty minutes or more.

Sigalert, California Highway Patrol, Traffic

CHP officers at traffic accident on Los Angeles freeway in Chatsworth. Photo from California Highway Patrol, West Valley Division.

For more information on Loyd Sigmon and SigAlerts, visit Harry Marnell's web site SIGALERT!

Also find Los Angeles area traffic reports, real-time speeds, accidents, and traffic cameras at SigAlert.com.

From a Los Angeles radio DJ reporting on traffic: “The 605, that demon freeway, ought to be called the 666!”