I am building a route and session and have laid a lot of track. I am using TS12 Build 49922. I am running all my consists via AI. When I go into driver it seems that some tracks go invisible. The trains just run on grass or whatever for a distance, then the tracks appears again. I suppose between different vertexes. When laying the tracks I set the vertex heights at 0.00. Should I be setting them at a more positive setting? If so by how much? Any help will be appreciated....Thanks....