MONTREAL -- As the closure of the Mont-Royal tunnel for REM work looms, the STM says it is renting coach buses to ease commutes into the city during the construction. 

The tunnel's closure will impede commuter train access to downtown Montreal during REM construction. Part of the REM line will begin running in 2021, with the full system scheduled for completion in 2024.

About 18,000 commuters take the train through the tunnel every day. 

The STM announced on Monday that it would rent 30 coach buses to run from Roxboro to Cote-Vertu stations and from Acadie to Mount-Royal and Namur stations. Other STM buses will run from Bois-Franc station to Cote-Vertu. 

The coach buses can carry 55 passengers each. Two hundred STM drivers are being re-trained to drive them. 

They will begin operating on Jan. 6, the same day the Mount-Royal tunnel closes. 

The rentals cost $2.9 million.