A communication systems failure that forced the TTC to suspend subway service across the city for more than two hours during rush hour on Monday morning was caused by a defective switch that drained the battery for the transit agency’s backup power supply.

According to TTC CEO Andy Byford, a power failure at the TTC's Hillcrest complex on Sunday night caused the uninterrupted power supply (UPS) to be turned on.

At first the UPS was able to supply power to the TTC’s critical systems and service was unaffected, but at some point overnight the battery powering the system was drained, resulting in the failure of the radio system train operators use to communicate with the control room.

The loss of power also impacted the TTC’s internal communication system, preventing the transit agency from sending out Tweets and emails to advise riders of the suspension of service on all four subway lines.

TTC officials estimate between 125,000 to 150,000 people were impacted by the subway shutdown, which began at around 5:30 a.m. and was not fully resolved until 7:35 a.m.

“I absolutely understand customer’s frustration. I am very disappointed that this happened this morning,” Byford told reporters on Monday afternoon. “Over the last two months I’d say subway service has been a lot better – we have had way less disruptions, we have added trains and the service has been running pretty well – but I know that all counts for nothing when you have a failure like today. Our reputation took a big hit.”

Ordinarily during subway closures the TTC will send shuttle buses to transport riders but on Monday Byford said the agency was unable to do so because it would have “decimated” the city’s bus network, which was “bearing the brunt” of the displaced riders .

Meanwhile, without shuttle buses to transport stranded riders, thousands of people were seen spilling out of subway stations and trying, often unsuccessfully, to flag down cabs.

At one point, Uber implemented its surge pricing, charging riders in some regions up to five times what it would normally cost them.

Speaking with reporters outside Davisville Station, Byford said he is committed to getting to the “absolute bottom” of today’s service interruption and as part of that will review the TTC’s response.

“Job number one is to replace that transfer switch. We want the technical people to look at it in detail and see what was it? Was it a one-off failure? Was it a systemic problem? We don’t know that yet,” Byford said. “Next, we need to look at how can we quickly separate the power supply to the customer communications system with the power supply to the communications that the drivers rely on because you cannot have a situation where we are not able to run a train service and can’t tell anyone about it.”

Tory says he still supports Byford

While TTC officials further investigate the cause of today’s subway shutdown, Mayor John Tory is publically supporting Byford and his handling of the crisis.

“I asked him this morning did you test the system? Yes. Did you have a backup system? Yes. Did you test the backup system? Yes. It is one of those things where what can go wrong will go wrong,” Tory told CP24 during a one-on-one interview late Monday afternoon. “He made the right decision to close down the subway. You couldn’t operate the airport without having radio communication between planes and you can’t do it with subway trains.”

As a result of this morning’s subway shutdown, Ryerson University and the University of Toronto Scarborough both delayed convocation ceremonies by an hour in order to give attendees more time to arrive.

In a statement issued earlier Monday, TTC Chair Josh Colle said the shutdown was “extremely frustrating” for everyone who relies on the TTC and promised to do his best to ensure it doesn’t happen again.

“It is deeply troubling that our system can experience such a major technical failure,” he said.

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