Race Interfaces

I have this racing game and to control distances, race completion and positions I've created interfaces, like invisible checkpoints.

The next step is to create teh AI for the non-player racers.

The racer is calculating his own distance to the next interface using Vector3.Distance(Transform origin, Transform destination);

But the Using Gizmos.DrawRay (or DrawLine) shows me that the distance is being calculated on a point I don't know. I wish I could use the center of mass of the interfaces (stretched cube meshes without colliders) or directly to it in the same Y position (ray to the front?).

On the screenshot below, you can see the ray being cast to a place outside the interface itself.

You can see tue next yellow interface and the white ray being cast to a place on the left, outside the track and the interface itself.

How can I calculate the distance to the interface directly in front of me or, even if I'am facing back, still calculate the distance to it.

The racer has that interface as a variable on his script.

After that, i must criate points inside each interface to use as a raceline. What should I use? Cubes? Stretched cubes to the top just like the interfaces? Single points?

Just to register, the players are floating 10 meters from the floor on a jetpack.