Toronto commuters will have to plan around a major subway outage this weekend.

The TTC has announced that it will be suspending service on the six Line 1 subway stations between Bloor-Yonge and York Mills for the entire day of Saturday, May 13.

During the outage, passengers will be forced to disembark subway trains at the aforementioned stations and switch over to dreaded Yonge Street shuttle buses, which will be operating to cover closed stations at Rosedale, Summerhill, St. Clair, Davisville, Eglinton, and Lawrence.

On Saturday, May 13, there will be no subway service on Line 1, between Bloor-Yonge and York Mills stations for work on the Automatic Train Control signal system. Shuttle buses will operate. pic.twitter.com/68tryR3QMZ

— TTC Service Alerts (@TTCnotices) May 11, 2023

The TTC states that the closure is planned to accommodate work on its Automatic Train Control (ATC) signal system, a new upgrade installed to reduce headways between trains.

Last September, the TTC proudly boasted the completion of that very same ATC. The close of that project was expected to be the end of a lengthy headache for weekend commuters that saw service frequently grind to a halt on Line 1 on Saturdays and Sundays as well as off-peak weekday hours from 2017 to 2022.

But the near-weekly closures appear to have resumed in recent weeks, as the completion of the ATC signal system was not, in fact, the final step in the project.

According to a TTC financial report issued in April, the project is currently in its sixth and final phase following the completion of the ATC signal system's installation and entry into service last year.

The current phase of ATC enhancements and the cause of the upcoming closure is targeted for completion by June.