The L.A. Marathon, being held Sunday morning, usually bring concerns about traffic and street closures.
But this year, there is an added issue: The beginning of daylight saving time.
Clocks should spin forward at 2 a.m. Sunday.
Tracey Russell, the marathon's chief executive, told The Times' Rene Lynch Friday that marathon officials have been doing everything possible to get the word out to competitors: "Remember to set the clocks forward an hour."
The street closures will be in various places in Los Angeles, West Hollywood, Beverly Hills and Santa Monica.
L.A. Marathon organizers warned that road closures will begin at 3 a.m. and be in full effect three hours later. Crossing the course will not be permitted. The race begins at 7 a.m., with streets reopening on a rolling basis as approved by public safety officials.
Freeways around Los Angeles County mostly will be unaffected by the closures, save for some ramps that will be shut down for several hours.
Officials in West Hollywood and other cities along the route are also sending out advisories to residents regarding street closures, and suggesting the public follow local official Twitter accounts for announcements as streets reopen.
There is also a map on Commuterama.com that is designed to help motorists avoid the closures and let those who want to cheer on the marathoners know how they can navigate the route.
Meanwhile, weather officials say Sunday will be partly cloudy, but warm.