"We're testing the train, so occasionally these trains will come up and down the tracks, and we want to urge the citizens that live in or around the Expo Line to be extremely careful," Los Angeles City Councilman Herb Wesson said.
Safety tests were performed Monday on the Expo Line, which will link downtown Los Angeles and Culver City.
There will be a car running east and west along Exposition Boulevard for the next seven months, officials said. They also warned against walking along the tracks.
It has been 50 years since any type of commuter train has traveled through that part of the city. Tracks from the old Red Car Line are being used for the new Expo Line. There will be 19 stops in all.
"It's a blessing to me because now it can help me get from point A to point B, especially with gas prices being high," said Floyd Sealy of Los Angeles.
In the long run, the plan is to get the Expo Line running to Santa Monica by 2015.
