The incident, which took place on Oct. 31, 2010, killed Dylan Ford, Mitchell Bracken-Guenet and Ricardo Conesa. Two other teenagers who were with them were not injured.
The coroner's report states the five young men were drawing graffiti near the entrance of the Turcot railway tunnel.
The report written by coroner Kristyna Pecko recommends Transport Canada reinstate the obligatory bright headlights for locomotives on trains.
The current guidelines allow train conductors to reduce the headlights' intensity in order not to blind drivers coming in the opposite direction.
According to an investigation by Radio-Canada's Enquête program last year, dimming the headlights nearly shuts them off completely, which could have played a role in the incident.
In her report, Pecko said the headlights were dimmed to about nine per cent of their maximum brightness.
CN Rail issued a statement saying the dimming of headlights is mandated by the Canadian Rail Operating Rules and serves as a way to "protect the safety of vehicular traffic by avoiding that drivers be blinded or distracted by locomotive headlights."
Jamie McAllan, the mother of one of the victims, said there was no fence near the Turcot tunnel at the time. She said the coroner's report should suggest tightening the laws on railway safety.
CN Rail said the public has its own role to play.
"Police presence and fencing cannot be viewed as the only solutions to trespassing. Ultimately, it is the public's responsibility to obey the law at all times."
Mylène Bélanger, spokeswoman for Via Rail, echoed CN's statement.
"It's everyone's responsability to remind our children about the important of rail safety and about the fact that it is dagerous. Tracks are dangerous," she said.
The coroner's report also suggests that organizations create campaigns to make people aware of the dangers of railways
In a statement released by Transport Canada, the department said it "recognizes the important role the Coroner's office plays in reviewing the case," and said it would examine the recommendations.