The TTC is exploring the idea of getting rid of its continuous trip transfer system in favour of a method that would allow riders to hop on and off public transit vehicles within a time limit.

The time-based transfer system is used in many cities and it has been considered before in Toronto. At Tuesday's meeting, the TTC's board will debate whether to implement the system and time it with the Presto card rollout in 2015.

In a report to the board, staff concluded it is feasible to do the switch and it would be easier to implement when Presto cards are used across the entire network, but commissioners must consider whether it would be a smart financial decision.

Because fewer return fares would be purchased, the TTC would suffer a $12 million loss in revenue with an unrestricted 90-minute transfer and a $20 million loss with an unrestricted two-hour transfer, said spokesman Brad Ross.

“It’s not cheap,” Ross told CP24 reporter Cam Woolley on Friday. “It would become an added budget pressure.”

Ross said the TTC would hope to fill in that gap with an increased subsidy from the city, although a fare increase could be looked at, as well.

Ninety-nine per cent of all transferring customers do so within 90 minutes of their first boarding and all transfers are made within two hours, the report says.

“With the exception of this revenue loss, all other aspects of a time-based system would appear to be positive for both customers and employees,” staff wrote in the report.

There are measures the TTC could implement to try to ease the financial blow.

Customers could be prevented from getting back on the route where the transfer was issued, but staff say that would make the system “less attractive” and it would be more complex to explain and enforce compared with an unrestricted time-based transfer.

Ross said the TTC is considering the switch because of repeated requests from customers, who prefer a time-based transfer because it would allow them to get on and off as they please while running errands and for short return trips.

“Customers have said for years they would like to have it,” Ross said.

The report says a time-based system would increase the number of customer journeys, meaning the TTC would have to boost service and it would likely need more funding from the city to pay for that.

The report also raises concerns about enforcement and security at unattended transfer-issuing machines at subway stations.

Time-based fares are currently used on the 512 St. Clair streetcar line. That system began as a trial about eight years ago and continued. The report recommends ending the trial if time-based transfers aren’t included in the TTC's 2015 operating budget.

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