In order to properly prototype an autonomous driving experience, I had to pull together many different free Unity packages and glue them together with custom code. This is that code.
The first file I had to edit was a speed controller to keep the vehicle from constantly accelerating. I named this file "woahBuddySlowDown" and added in some items to limit the vector speed of the rigidbody - in this case, the car. Later, I found this was also useful for controlling the speedometer (since it reads the speed of the vehicle), so I used it for that too with some help from CodeMonkey.
After that, I edited the Vehicle Controller from Unity to take input from the wheel controller. It wasn't a huge edit.
Then, I set to work editing the code from the PathFollower package, which is provided for free by Sebastian Lague. This is where I edited the most, including three states, a way to toggle between them, and a way to follow the path only on the X and Z positions so the Y position could be simulated with gravity. This was the most difficult part of the project, but also works well enough to be considered a success!