But building a bypass seems to be still hit-and-miss. Sometimes the bypass I build is recognised, and I can then remove the old road.

But sometimes it isn’t. And I would like to know what I should do so that the bypass I build is actually recognised as such. What is the requirement for the bypass? And can I replace two streets with one bypass? I often like to build a road tunnel, and then a station on top of that, so that the city can develop on both sides, and roads are not in the way of any tracks I want to build.

So what should I consider when building a bypass so that the system recognizes it, and allows me to remove the old roads?