A big rig that crashed onto the Gold Line tracks on Thanksgiving morning, damaging signaling equipment, will force trains to travel at lower speeds until repairs are completed in December, a Metro spokesman said.

“Due to the tractor-trailer crash yesterday (Thursday) morning, riders on the Gold Line should expect to experience delays of up to 15 minutes for the next two weeks,” said Brian Haas, Metro spokesman, in an email Friday.

“While the semi did not damage the tracks or overhead power lines, it did destroy a signal case, which helps regulate the speed and spacing of the trains,” Haas said.

Riders already were experiencing slower commutes Friday.

“Yes, it is going very, very slow, like two miles per hour from Sierra Madre Villa,” said Ed Serrano, a Pasadena resident. Serrano got off the train at Lake Station and said the reduced speeds added about 10 minutes to his train ride.

Trains will be traveling much more slowly between Sierra Madre Villa and Lake stations in Pasadena, where the signaling equipment was damaged by the crash, Haas said. The trains were staying at the affected stations longer on Friday in order to keep the correct spacing. The slowdown will keep trains spaced apart, a function performed by the signaling equipment before the semi-truck careened over the 210 Freeway median onto the tracks.

Also, Gold Line riders starting Monday, from 9:30 a.m. until 2:30 p.m., will see trains arrive only every 15 minutes due to scheduled maintenance. Trains will share one track in the Chinatown area, Metro said.

The crash in east Pasadena occurred at 1:55 a.m. Thursday, disrupting train service between the Allen Avenue and Sierra Madre Villa stations for close to nine hours, Haas said. Metro re-opened the Gold Line just before 11 a.m. Thursday.

Repairs to the signaling equipment are being done at night in order to minimize delays, Haas added.

Gold Line riders starting Monday, from 9:30 a.m. until 2:30 p.m., will see trains every 15 minutes due to scheduled maintenance. Trains will share one track in the Chinatown area, Metro said.

The semi was traveling westbound on the 210 Freeway when, for unknown reasons, it swerved and crashed through the center divider and blocked the tracks, according to a California Highway Patrol incident log.

Crashes onto the train tracks, which run along the middle of the 210 in the eastern section of Pasadena, have become a re-occurring problem. Crashes onto the tracks adjacent to the 210 are happening once every 10 months, Metro reported. On Oct. 13, a big rig breached the center divider of the 210, landed on two train tracks near Madre Street and caught fire, disrupting Gold Line service.

In July, a LA Metro committee voted to early double the height of the concrete barriers in an effort to prevent trucks and other vehicles that breach the barriers from disrupting service. The redesign will take up to three years at a cost of $11.08 million.

City News Service contributed to this article.