Sig Alert
（重定向自SIGalert）
A Sig Alert is defined by the California Highway Patrol (CHP) as "any unplanned event that causes the closing of one lane of traffic for 30 minutes or more". CalTrans uses the term "SigAlert", and is defined as any traffic incident that will tie up two or more lanes of a freeway for two or more hours. Sig Alerts are issued by the CHP and are posted on their website, broadcast on radio and television stations throughout California, and signaled to motorists via electronic message signs on the freeways. The term was added in 1993 to the New Shorter Oxford English Dictionary. (In practice, there is no standard spelling; the CHP Web site uses "SIG Alert", "SigAlert", and "Sigalert", all on the same page.)