TTC riders who use the subway between Bloor and Union stations will be relegated to shuttle buses this weekend thanks to a two-day closure for construction.

Train service will be suspended on the affected part of the Yonge line on Saturday and Sunday. Shuttle buses will run that route instead, while trains will resume at 6 a.m. Monday.

Subway trains were already moving slower than usual through the affected stations on Friday, as crews in the tunnels prepared for the weekend's work.

Workers will continue the installation of a "crossover" track that began a few weekends ago, designed to allow trains to reverse direction about 100 metres south of College Street in cases of emergency.

"If there's a mechanical problem or delay on the line, instead of having to turn back trains at Bloor and Union stations, this allows us to turn back trains at College," TTC spokesperson Danny Nicholson explained to CTV Toronto on Friday. "In the event of a disabled train or other emergency, it means less problems for our customers."

The weekend closure is the second in a series of three on that stretch of subway tracks. The final phase of the crossover construction will occur the last weekend of March.

While most track repair work is done overnight, the TTC says the magnitude of the installation necessitates full weekend closures. About 225,000 riders use that section of subway on an average weekend.