Actually, do you have Prop & Tree Anarchy? If not, then that's why they disappear. Without the mod props and trees disappear when you place a road over them. And placing any other roads nearby or perhaps terraforming will update the area hiding any trees or props that collide with a road.

More Beautification to place props in the city, MoveIt to tweek placement and Prop Snapping to move props up and down.

It prob shows the reasons why we can't place props and things in the game without mods. :P It's prob best to move/remove the prop while doing all the terraforming and then place it again when the area is ready for it. There really isn't anything I can do to make it behave better.

@Weed Exterminator: Modifying terrain with props placed is always gonna be messy, there really isn't anything I can do about that. If you have trouble with them jumping up higher than you want them, then there's on option in Prop Snapping now to enable props to be lowered into the ground. Be careful though if you terraform with that on since I guess the props can disappear into the ground completely.

These are awesome, great work :D

Yes!! Perfect for Trains too :DD

you are really on fire with your overpass walls... thanx again for this new version.