In the picture I left at the bottom, you need to make the configuration setting, 
otherwise the car will be thrown out of the game, 
this setting allows the game to increase the buffer size.


/Computer/Documents/Euro Truck Simulator 2/Config.cfg 



uset r_buffer_page_size "10" (OLD) 
uset r_buffer_page_size "30" (NEW)

you will get a value of 10, you will need to make it 30.