TORONTO -- TTC staff are recommending that the Scarborough RT be decommissioned and replaced with buses by 2023, a full seven years ahead of the expected completion date for the Line 2 subway extension.

Staff were considering three different options on what to do with the increasingly derelict rapid transit line, including a partial overhaul that would have allowed it to remain in service until 2030, albeit with fewer trains and the associated need for supplementary bus service.

But in a report that will go before the TTC board next week, staff rule out overhauling the SRT due to the costly price tag of $522.4 million and the “high risk of not achieving the required service reliability.”

Instead, staff say that the TTC should shut down the line in 2023.

They are proposing two options for further study on how to provide supplemental service while the subway extension is completed.

Both would see eight bus routes that currently terminate at Scarborough Centre Station provide express service to Kennedy Station for at least seven years.

The cheaper option would cost about $357 million and would see the TTC use buses from its existing fleet for the first three years and then purchase about 20 news buses a year to maintain the enhanced service between 2027 and 2029.

The other option would cost $374 million but would allow the TTC to immediately purchase new buses to help provide the enhanced service.

“Both options are a low risk option from a cost, schedule, and deliverability perspective,” the staff report notes.

The report says that commute times will increase as a result of the switch with the trip from Scarborough Centre Station to Kennedy Station taking 15 to 18 minutes rather than 10.

But it says that any increase in commute times will be partially offset for the 75 per cent of riders who currently transfer from buses to the RT and will not longer have to.

The report also makes clear that keeping the RT in service until 2030 just isn’t an option.

It says that the trains used on the line reached the end of their life cycle a decade ago and that the “obsolescence of key parts” is becoming an increasing issue.

The vehicles are also breaking down more frequently with the staff report suggesting that there will be approximately four major delays per week by 2026 if it is kept in service.

“As the overall vehicle reliability continues to degrade with equipment failures, it would result in more frequent and unscheduled service interruptions, negatively impacting service level. Consequently, sufficient trains may not be available to provide the required service, and passenger crowding would get progressively worse over time to a point where it may not meet the minimum service level,” the report warns.

This is a developing story. More details to come.