Great progress, sorry I couldn't find time to reply recently.
Here is method on how to merge "low poly" edge with "subdivided" road mesh edge, as I have been doing with Targa florio:
(I use blender v2.8+ for example)
Step 1: Select the
2 connected node of "low poly" edge,
Step 2: Right click mouse and select
Subdivide, then set amount
cuts that match the road mesh edge,
Step 3: Enable snapping (vertex), then just select each node and move close to the road mesh node and will snap onto it. Repeat this until you fixed all gap (this is very time consuming unfortunately),
------------------------------
However, there is a slightly easier way, what you need to do first is:
Step 1: Select the each node of "low poly" edge, and snap them to the
nearby "subdivided" road mesh edge,
Step 2: Select the
2 connected node of "low poly" edge, and subdivide them (that match the amount road mesh), then select all those nodes and Press "m" > "By distance",
Step 3: you will need to adjust the value of "Merge distance" until all the nodes merged together,
--------------------------------
For road noise, what I usually do is:
Step 1: Select all subdivided road mesh nodes, but deselect all the edge nodes, this way will make sure that edge will not be distorted by randomization; then right click mouse and select
Randomize Vertices,
Step 2: adjust
Amount value until you feel good,
Step 3: This is an optional step (as I have used this method for targa florio and willow spring), instead of randomize every node, you can partially select some of the nodes to perform
Randomize Vertices, which may help bring more variation (as you can repeat this progress multiply times with different amount selection and randomization),
Good luck.
Edit: Here is also a great tutorial by LilSki for adding advanced road bumps (
https://www.racedepartment.com/thre...n-track-making-plus-tips.122794/#post-2256509 )