There are two parts to that.
The first is that trains have been rolling to Prince Rupert with flammable liquids for many years. There has been a systemic increase in standards around key trains, which are trains carrying dangerous goods. There's been a systemic increase in standards for high-risk key trains. The kind of trains you're talking about qualify.
As part of those higher standards, when there is a change in operating, including greater volumes, there's a requirement to update the risk standard. There have been risk assessments, standards and measures put in place for years. Now there's a regulatory requirement for CN to provide an updated risk assessment and for Transport Canada to assess that, but that's not the first step in the safety process. There have been many steps before that.