Many video/written tutorials to help you with many different parts of track creation. If you found them useful, consider telling the tutorial author and give them a "thumbs up".
rFactor 2 - Guidelines for artists (for DX11 release)
Race Track Builder - How to make Racetracks for Assetto corsa by Nukedro
Have you found a great tutorial that has helped you with your track modding?
Conforming road onto arbitrary surface (3dsmax) by Xoio
Making roads (3dsmax) by akila uyanwatta
Road modelling (3dsmax) by TheHellsing99
Track Mesh from splines (3dsmax) by freew67
Building complex road and terrain (3dsmax) by Benjamin Joel
Smoothing track mesh (3dsmax) by C3lloman
Creating high detail 3D terrain - Google Earth (3dsmax) by Temanibble
Topography from Google Earth (3dsmax) by Nathan Melenbrink
Scan and import a terrain from Google Earth (3dsmax) by AsuniLands
Create Realistic Terrain from Autocad to 3dsmax by Arch Viz Camp
Google Earth Capture - Site With Textures - Fast Context Model Generation (3dsmax) by Paul Fatkins
Realistic Terrain (3dsmax) by TheArtOfTheGame
Generate terrain (3dsmax) by AUKAN Studios
Terrain (3dsmax) by pazz the pazz
Generating Terrain (3dsmax) by Denis Keman
Make a Quixel Colors Button - Quick and Simple (www.quixel.se) by DEMOCALIBER
PBR Texturing in Quixel Suite 2 for ArmA 3 Building by Obsidian Games
UVW Channels and Tiles (3dsmax) by Aaron Dabelow
Rendering Ambient Occlusion with Scanline Renderer in 3DS Max
Modeling tires and baking normal map for low-poly version (3dsmax) by 3D Tutorials AM
Creating City Blocks - Part 1 - Introduction by Autodesk 3ds Max Learning Channel
Environment Modeling #2 Procedural Stone, Stone. Mapping and painting by SaschaHenrichs
PropLine - distribute props and models along spline by Shawn Olson
Clothes Tutorial (3dsmax) by Tutorial Bone Yard
Populate Tree Leaves using Particle Flow (3dsmax) by Ragdoll Studio LLC
Character Animation Toolkit CAT (3dsmax) by 3D Tutorials and News
Rigging a Character 3D Model - Setup of the Cat Rig & Skinning (3dsmax) by The 3D Tutor
Tutorial "Biped Animation Basics" Part 1 -3DS MAX by DarkSaintStudios
Garage Door Rig (video of door in action)
Biped movement files and skinning (3dsmax) by Shawn Shoptaw
Creating crowd simulation (3dsmax) by sanvfx
Rigging Tutorial HD: "Characterization in MotionBuilder" by The CGBros
Animating a tree (3dsmax) by Dave Jones
Wind effects on trees (3dsmax) by CAD Studio
Blowing leaves in the wind (3dsmax) by fortres008
How to use Animation Cache (3dsmax) by Marvelous Designer
Point Cache modifier (3dsmax) by sanvfx
How to loop a point cache animation (3ds Max) by 이상원
Rigging & Animation - Character Generation - Character Generator to Biped Mocap by Gary M. Davis
Basic character animation modification (in ZModeler) by ZModeler3
4 - Basic road modelling, material settings, mapping, exporting...
5 - Basic terrain modelling, material settings, mapping, exporting...