Once again, the TTC union is warning Toronto that a strike could be in the cards.

The threat comes from a proposal we first told you about back in June. But now it seems the city is getting serious.

TTC brass will decide Thursday whether or not to randomly test their employees for drug use. It's a plan that has the mayor's support - on one condition:

"I have a significant concern with random testing," David Miller acknowledged Tuesday.

"I think its management's job to oversee workers and to make sure the public is safe and it's completely appropriate to test people if there's some reason to believe they're doing something improper," he added.

Unlike Miller, Councillor Michael Thompson seems to be in favour of sporadic testing.

"I think the random testing provides a deterrent firstly. Yes, it is very complex. It's controversial. The question is how do we ensure that the workers are safe and our passengers are safe?" he explained.

The testing would affect drivers, maintenance workers, mechanics, and some managers. Prospective employees would also be subject to a scan. The Toronto Transit Commission says it's an issue of public safety, while the union argues it violates the workers' rights.

"We are adamantly against any form of testing. We believe it's invasive," argued Bob Kinnear, president of Amalgamated Transit Union Local 113.

"I think all of us understand people's right to privacy as well. I'm sure the Commission will debate that," Miller countered.

The plan was put into motion when the TTC found that over the last three years, there have been 39 incidents involving the use of drugs and alcohol with employees.

"We're not trying to blame anyone. We know that there is a problem. We know that the numbers are going up, and we need to address that," outlined Thompson.

It's an accusation Kinnear flatly refutes.

"We're not quite sure where the TTC gets those numbers. Our information does not reflect that," the union boss spat.

And he's adamant the measure will not succeed.

"We have protections, we have laws in this country that I don't want to lose and I don't want to be dwindled," Kinnear stated.

That will be debated later in the week behind closed doors. What do riders think of the plan?

"I think it's a good test," supported one man.

"They work for the city, right? And I mean they have responsibilities not to themselves but to everybody else."

Meanwhile, another Toronto citizen was in favour of more targeted testing.

"Maybe it's specific people," she said.

Even if the proposal is carried, it won't take effect for another year.

Check out some myths and facts on drug testing and find out how labs conduct the tests.

TTC Reportedly Considering Drug/Alcohol Testing For Workers