Hello guys. I’d like to share with what I found, maybe it will help you with your game. I experienced many game crashes durning long races and disappearing parts of the track. What I noticed, thanks to my MSI Afterburner, GPU RAM usage was every time at maximum(around 4GB). I tried to lower game resolution scaling to 85-90% and lower track resolution to low, what caused GPU memory to drop a little bit to level of 3,8GB and I was surprised. There were no more crashes or artifacts durning race.
What I also noticed, once my GPU memory usage came back to maximum at one race in GT3 class and caused one more game crash. I was searching what else I can do without losing graphics quality. What is it? You will not guess 
I just disabled option that alowed other drivatars to use player’s projects. RAM Memory usage droped by another 0,2-0,3GB and I was able to complete whole race.
So, if you are experiencing crashes durning the race, try to verify your GPU Memory usage and drop settings for scalling and track textures resolution. Also, disable other drivatars projects in drivatar settings. You don’t even have to start race to verify this. I noticed, that memory usage is set in pit lane before you even start the race and it won’t change at all after you click start and durning race. I hope it will help you.
One more thing, if you change graphics settings durning race(or in pit lane), memory usage will drop lot (around 0,5GB or more), but if you will reload race, it will rise again by 0,2-0,3GB. It’s good idea to exit race and enter it again after every change to check uage.
My setup:
Crucial 256GB SSD
Intel Core i7-4770k
Asus Strix GTX 980 (4GB)
16GB RAM DDR3