Protective shields are being installed on almost 1,000 Edmonton Transit buses as new statistics show that violent incidents against bus drivers are continuing to creep upwards.

Of 65 violent incidents in the first nine months of 2019, 78 per cent were punching or spitting and five per cent involved a weapon, according to a monthly report compiled by the city.

"Last year, there were over 70 [incidents]. It's been gradually going up and up and up," Mark Tetterington, president of Amalgamated Transit Union Local 569, told CBC Radio's Edmonton AM on Thursday.

"I don't know whether it's people out of work, if it's mental health issues, I don't know. But it's getting worse and worse and worse," he said.

"It can only be a matter of time before someone gets killed, like in Winnipeg a couple of years ago. We don't want to see that happen here."

This week, the city began installing retractable tempered glass shields on Edmonton Transit's fleet of almost 1,000 buses. The shields are part of about $20 million in transit safety and security enhancements approved by the city one year ago.

About 30 shields will be installed each week. The project is expected to be completed next fall.

Tetterington said the three-centimetre thick shields, which he described as "the latest and the greatest in technology," stretch almost up to the ceiling.

An opening slightly bigger than a car window will ensure drivers can still interact regularly with passengers, he said. It's expected that drivers will normally keep the window open.

"If a driver feels like they're threatened, or if they've picked up a customer they've had a problem with in the past, they can just raise that shield up," he said. "It takes about 2½, three seconds for it to raise up, just like a regular car with a car window.

"Where [it's] a punch or whatever, you can see that coming. Our operators get to know their patrons pretty good. You get to know if someone's going to be problematic when they get on the bus."

A bus driver is not supposed to intervene in confrontations between passengers and should instead contact Edmonton police or transit security, said Tetterington.

In September 2018, an Edmonton Transit operator was stabbed more than a dozen times at the Mill Woods transit centre.

According to the statistics, one-quarter of all incidents against bus drivers are directly related to "customer behaviour." Fare disputes are the biggest factor, at 31 per cent, while 28 per cent are unprovoked.

The report includes detailed descriptions of seven incidents that happened in September.

In one example, a passenger reluctantly paid the bus fare after being told he couldn't ride free. "A short time later, the suspect approached the [operator] and swore at and spat on him before leaving."