MONTREAL -- Starting Monday, Quebecers will be wearing masks on buses and metros. And that’ll be a big difference to many people, since it’s estimated that right now, only one out of every two people on public transit is wearing a mask.

The question, though, is how exactly will it be enforced? The union for STM bus drivers says its members don’t want to play police, and besides, exactly what behaviour will be illegal is still not entirely clear.

The STM says it’s going to figure things out as it goes while also seeking clarity from the province on some points.

"We don't have any answers for you today, but you're right, it might pose some difficulties,” STM chair Philippe Schnobb told CTV News.

One issue still left to sort out: it hasn't been decided if people won’t be allowed onto transit without a mask, or whether they can also be fined for taking the mask off during the ride.

"That's a good example of how difficult it is,” said Schnobb. 

“If someone gets into a metro station with a mask and takes it off in the car, you might understand that it will be very difficult for someone in charge at the STM” to know how to respond, he said.

Officials are hoping that Montrealers decide to comply and make their jobs easier.

To further smooth things over, the STM plans to hand out 1.5 million masks between now and September.