Thank you for the question. I'd like to talk a little about crossing safety.
My previous role at CN was as chief signal engineer. I'm intimately familiar with crossings, and they are one of the areas where we have substantial opportunity to improve safety, so I appreciate the opportunity to talk about it.
Your question is when would we build a grade separation, either a tunnel or an overpass. Certainly there are significant economic considerations there, especially when you try to build infrastructure in an urban environment; the costs become prohibitive very quickly.
On the crossing side, there are a number of alternatives. Eliminating a crossing is always the safest way to prevent crossing accidents. The Railway Research Advisory Board has done a lot of work and has sponsored a lot of research on crossing protection and improving crossing safety, considering whether cheaper crossing technology exists, not for urban areas but for rural areas. Driver behaviour is certainly one of the key considerations, as is pedestrian behaviour. Device conspicuity—how easy is it to see the crossing devices?
In addition, on that same CN line we installed some second train warning signs to see if that would be an effective warning to people that a second train is coming. We've had incidents when the first train goes by and people make the assumption that they're okay to go. It's a multi-track territory and there could be a train coming on the second track.
So I think there are a number of things we can do to improve crossing safety before we take the fundamental step of investing the significant dollars to do a crossing elimination, although speaking as a railway person, the safest crossing is the one that's not there.