Metrolink will suspend all service for four days starting Tuesday so workers can clean and repair trains and upgrade the regional rail network.

Metrolink trains will be out of service from Tuesday through Friday, resuming regular service on Dec. 30. The closure applies to the entire Metrolink system, including the Arrow service in San Bernardino County.

Metrolink officials called the suspension a chance to complete repair and upgrade efforts to ensure “safer, more efficient service.”

“Placing our system temporarily out of service was necessary to complete the final phase of a three-year modernization project at LA Union Station, which connects six of our seven lines and serves as the agency’s central hub,” Metrolink’s Chief of Program Delivery Justin Fornelli said in a statement. “We’ll be upgrading the signal system where trains enter and exit the station, but we’re not stopping there. This unique break in service will allow us to tackle state-of-good-repair projects across multiple lines, as we work to deliver the safest, most reliable passenger rail experience possible.”

Metrolink officials said the work will include replacement of 1930s-era signal-relay technology, which will allow the agency to run multiple trains on multiple tracks as they arrive and depart from Union Station, decreasing delays and improving safety.

Crews will also make concrete repairs on train platforms and perform thorough cleanings, while adding more lighting in Union Station tunnels.

Track improvements will also be made on parts of the Antelope Valley and San Bernardino lines.

Metrolink is not providing alternative transportation. Amtrak’s Pacific Surfliner will continue operating during the closure, but those trains will bypass Union Station.

LA Metro buses, subways and rail lines will continue normal operations during the closure.