Sigmon resumed his job in Los Angeles after the war, rising to the position of Executive Vice President with Gene Autry's Golden West Broadcasters, which owned eight radio and two television stations on the west coast, including KMPC.
In 1955, Sigmon invented a specialized radio and tape recorder that the Los Angeles Police Department used to alert radio stations throughout the city to traffic conditions and emergencies. The messages were referred to as "Sigmon traffic alerts," a phrase quickly shortened to "Sig Alert." The system, now employed throughout California, has been copied in numerous other areas.
Loyd Sigmon received recognition and honors from local and state government agencies, the National Safety Council, and broadcasting and radio organizations. In 1998, when the California Department of Transportation (CalTrans) and the California Highway Patrol opened their Freeway Traffic Center in Los Angeles, Sigmon attended as their special Guest of Honor. He was quoted in the Los Angeles Times as saying, "I ran a multimillion-dollar corporation, but it's the Sig Alert that people remember me for."
Sigmon kept his ham license, W6LQ, current even after retiring to Oklahoma.