how to implement mini map

The easiest, but also potentially the most expensive in terms of performance, is to add a camera that looks down on your terrain from a height (higher is zoom out, lower is zoom in), then render it to a texture. The camera can be made a subobject of your main car so it will follow your car.

you can make an image to duplicate your track, then using this image to render it on the minimap section, make a dot or a player in the minimap follow the movement of your car on your 3d world just using the coordinates on the XZ axis (assuming you will see the minimap from above) on each update change the value of the player indicator on the minimap getting the values from the real car, thats other way to do it, instead of the camera thing hope this answers helps you