Installing safety barriers on Toronto's subway platforms could take 15 years, the TTC says after two boys were pushed in front of a train, spurring calls for the devices.

Such a barrier would span the length of the platform to prevent anyone from getting near the tracks, TTC general manager Gary Webster told the CBC on Monday.

When a train comes into the station, doors would open in the barrier at the same place as the train's doors. The passengers would get on, he said, then both sets of doors would close again before the train moves on.

But first, the city has to upgrade the subway's signalling system. "You need to actually be able to stop the train at a precise point on every platform," said Webster, so the train's doors are lined up with the doors in the barriers.

Target date: 2016

An upgrade to automate the system is in the works on the Yonge-University line, Webster said, but it isn't due to be completed until 2016.

TTC chairman Adam Giambrone said it would cost hundreds of millions of dollars to computerize the trains so they stop at the same location every time.

In 1997, Charlene Minkowski, 23, was pushed to her death in front of a subway train at Dundas Station.

In the most recent incident, three boys were pushed and two fell on to the tracks during the Friday afternoon rush hour. Pushing incidents, Webster stressed, are "a very rare occurrence."

One teen suffered minor injuries

The 14- and 15-year-old who fell survived by rolling under the edge of the platform as the train came into the station, police said. One suffered minor injuries.

Adenir DeOliveira, 47, faces three counts of attempted murder and two assault charges. He appeared in court Saturday and was ordered to undergo a psychiatric evaluation.

"What we need to think about in the meantime," Webster told CBC Radio One's Metro Morning, "is from a customer's point of view … how do you minimize the likelihood that you're going to be faced by the random act of someone pushing you to the subway?"

So far his answer is that people using the TTC need to remain aware of what is going on around them when they are in the subway system.