Lots of things probably changed under the hood for 3D in the transition from GM8.1 to GMS. Not surprising that you'd see some behavioral changes.
3D is a pretty gritty topic for GameMaker. If you want effective help when you ask questions you need to provide lots of context and post the game code that you think contains the problem. "The road is missing" tells us nothing about what is going on. We don't know how your road is supposed to work and how you tried to implement it, so we can't help you troubleshoot.
That being said, there are lots of things to check for the road. Is the texture a power of 2 size? Are you drawing it in the correct z location? Are you applying any 3D transformations to it? Concerning the car, if I remember correctly, old GameMaker versions had a "background color" in sprite images and you would check a box to say something like "my background color is black, so make black transparent when this sprite is drawn". In GameMaker studio, there is no "background color" and create the sprites with transparency already present in the sprite editor. If that's the issue then you just need to erase the black in the sprite image.
