A TTC driver has tested positive for being impaired while on duty, marking the first time a vehicle operator has run afoul of the transit agency’s new random testing policy.

TTC spokesperson Brad Ross confirmed that the operator was tested for drug use during a shift Saturday and the test, which takes several days to process, came back positive Wednesday.

As is agency policy, Ross wouldn’t disclose the substance the employee tested positive for, or say specifically what job the person held. It’s not clear if the worker is a bus, streetcar or subway driver. The person has been suspended pending the outcome of a disciplinary meeting with a supervisor.

Ross said many positions at the TTC involve safety, and it is important all workers are drug- and alcohol-free while on the job. But he said he understands the public perception “that, if somebody is driving, they have that extra responsibility.”

“It is concerning to us, whenever we have a positive result. And this is the reason why we introduced the policy,” he said. “The vast, vast majority of our employees come to work fit for duty and would never think or dream of doing anything but.

“But when it happens, it’s incredibly serious.”

In addition to the operator, another employee tested positive for alcohol use last week, Ross said. The staff member was not a driver.

The random testing policy went into effect May 8. Since then there have been eight positive tests, two for alcohol and six for drugs. The very first employee tested failed a breathalyzer. More than 300 employees have been tested so far.

One of the eight employees was a supervisor or manager.

The TTC says the tests only detect whether someone is impaired at the time, not whether they use drug or alcohol while off-duty.

More 10,000 of the TTC’s employees are eligible for testing, as they hold “safety-sensitive” or other designated positions. Executives are not exempt from the policy. Ross revealed that TTC CEO Andy Byford was randomly selected two weeks ago. He passed.

The TTC’s largest union did not immediately return a request for comment Thursday evening. In the past, union leaders have asserted that drug and alcohol use is not a systemic problem in the transit agency’s workforce.