In fact, in Vancouver that's exactly what happened. We did a whole corridor analysis and identified which ones actually needed to be grade separated.
Because you can't be grade separating all over the place, what we did was selectively pick the roads that were busiest, and we're grade separating those. A couple of them are being closed and a couple of them are being connected through what are called access roads that are sort of parallel to the rail track, and then you go to the next busiest road.
So not in all cases do they need to be separated, and you have to be wary of how many grade separations you're building one right after the other. They're very expensive.