I think there are two issues, probably both without a solution for now, but maybe anyone has an idea?

 

1. Flickering roads.

Parts of roads seemingly can't decide if they're on or below ground, resulting in flickering road textures. This happens often, almost everywhere. I don't know if it is an issue with the HD Mesh or X-Plane itself, but somehow the height data doesn't seem to match. It could also be a graphics driver issue (Z-Buffer).

 

2. Trees on roads.

Don't know why roads don't exclude anything else, but I get trees growing on highways ect. Also not sure if it is caused by the HD Mesh.

 

 

I've seen both issues and I think the first one is caused by a longer segments of road that don't drape correctly and end up going into the terrain (It happens in the default scenery as wel). The second issue is because some of the highways in X-Plane are surrounded by trees, so if you have a dual carriageway or motorway made up from 2 roads (as it is in OSM), then you end up with trees all over the road. This happens a lot on the roads in the UK and NZ because of the left-hand sided traffic

 

The trees I removed using a library object but I accidentally added it to world-models and made a few people angry as they couldn't work out where some of the trees had gone. I solved the first problem in my own sceneries by adding more nodes into the road (but this isn't a global easy fix)