The Toronto Transit Commission will conduct random drug and alcohol tests on employees starting next spring.

The TTC gave formal notice to its four unions Thursday, saying testing will begin March 1, 2017. The plan was approved at last week's TTC board meeting, despite criticism from the union representing transit workers.

Bob Kinnear, head of the Amalgamated Transit Union Local 113, argued the real danger to driver and passenger safety stems from long hours and split-shifts rather than drug or alcohol use. He said drivers often work up to 70 hours a week.

Right now, the TTC tests employees for drug use when they're hired, if there is "reasonable cause" to believe they are impaired, after a collision,and after employees declare they have a dependancy and have been treated for it. Employees can also be retested if they were found to be impaired after a workplace incident and are coming back on the job.

In a statement released Thursday, the TTC said there has been a 200 per cent increase in workplace impairment and test refusals from 2011 to 2015 and an 80 per cent increase from 2014 to 2015 alone.

This year, there were 21 cases of positive or refused tests before Nov. 30.

"This is not acceptable and the TTC cannot wait any longer to act," the statement reads. "The safety of its employees, customers and all road users —motorists, cyclists and pedestrians — is paramount in all that it does."

The transit commission says more than 10,000 employees will be subject to tests, including vehicle operators, maintenance workers, supervisors, managers and executives. A third-party provider will generate a random list of workers and conduct the tests on the TTC's behalf.

A breathalyzer will be used to test for alcohol and an oral swab will be used to test for drugs and prohibited substances like marijuana or cocaine. The TTC says the technology will only determine whether or not the employee is impaired at the time of testing.

The program will cost the TTC $1.3 million.