An assault on a female bus driver in Vancouver this week has the union representing transit operators calling for better police presence on city buses.

On Tuesday, three young women allegedly attacked a female bus driver on the 1000 block of West Broadway after they were asked to leave the bus for drinking stolen liquor and being disruptive. 

Transit police say there has been a significant increase in violence against bus drivers. Since January alone, they have received 52 reports of violence, 19 of which are assaults under criminal investigation. 

Transit Police spokesperson Anne Drennan suspects this number is low because violence is often not reported.

"Very often the drivers will be involved in harassing situations — where they're being yelled at, sworn at, that kind of thing — and they will pull into the next stop and the guy will jump off the bus. The driver then feels that rather than call transit security or the police, and report it right then and there, he will carry on with his route because he's got a bus load of people," said Transit Police spokesperson Anne Drennan.

Now the union representing transit operators, UNIFOR Local 111, is calling for police to be more fairly distributed throughout the transit system.

"We've been trying to get TransLink to shore up the resources in both security and transit police, because really where the physical presence is required: on a bus, on a bus loop," said union president Nathan Woods.

The problem, says the union, is that the public-private partnership that built the Canada Line has a contract requiring a high-level of police protection: 12 transit officers out of the 26 or so on duty at any given time throughout the Lower Mainland.

Transit Police did not confirm this requirement exists. 

'Impossible' to have police on every bus

Transit Police spokesperson Anne Drennan says the increased violence against transit operators is unacceptable, but there is only so much the 167-member force can do.

"It's very difficult. there are approximately 1,400 buses running in the system at any given time. You can imagine that makes it virtually impossible to have a police officer, for example, or security on each and every bus," said Drennan.

She also said when and where violence happens is hard to predict.

"Many of these things just happen kind of spur of the moment, and so you just don't know what route, what bus, what time of day."

Drennan said she knows the transit union would like more officers on bus routes, but it will never be doable with the current size of the force.

There is, however, one possible solution to prevent violence against divers and passengers. 

A new smartphone application is being launched at the end of March that transit users can use to report violence on the system. Alternatively, passengers will be able to text a new phone number. The alert will dispatch transit police, or the closest police force, in hopes of catching perpetrators.

With files from the CBC's Eric Rankin