In anticipation of students returning to school, the Toronto Transit Commission said on Thursday it is recalling some of its laid off operators to increase service.

In a news release, the transit agency said 150 of 450 operators who were temporarily laid off in April following a significant drop in ridership due to schools and businesses closing as a result of the COVID-19 pandemic have been called back to work.

"These have been difficult times for everyone at the TTC as we've been forced to respond to the pandemic by making some tough decisions to reduce expenses and revise service delivery," said CEO Rick Leary.

"The good news is that things are turning around and we're able to start bringing back operators and reinstating some of the service as well as adding service to the busiest routes across the network."

Before the pandemic, the TTC said it was carrying 1.7 million riders on a typical weekday. However, at the height of the pandemic, the transit agency saw the ridership drop to 15 to 20 per cent of pre-pandemic levels.

The TTC had said the layoffs were part of cost-saving measures by the agency to maintain transit service across the city. It has kept service at 80 per cent of regular levels throughout the pandemic.

As more businesses reopen as part of the province's Stage 3 reopening, the TTC said daily ridership has increased to 35 to 40 per cent of what it was prior to the COVID-19 pandemic.

All laid off operators are expected to be recalled when the TTC reaches 50 per cent of pre-pandemic ridership levels, the transit agency said.

"I want to thank Mr. Leary and all TTC employees for working with the City of Toronto to keep transit operating during the pandemic. The unprecedented ridership drop was no fault of the TTC and I'm proud to have secured hundreds of millions from the federal and provincial governments to help protect our transit system," Mayor John Tory said in a statement.

"The changes announced today will ensure that as schools reopen and more people return to work, the TTC can continue to deliver safe and reliable service across the city with increased service on its busiest routes."

Earlier this month, the province announced that the city would receive $404 million of transit money as part of the federal-provincial COVID-19 aid program.

According to the TTC, the ridership grows by up to 10 per cent between August and September in a typical year.

"But with so much uncertainty about what ridership will look like after Labour Day, the TTC is preparing to respond to additional demand with increased service as needed until full service is restored," the agency said.