I have a quite advanced top down car game and i use masks to detect collisions. I have the actual designed track (what the player see) with fancy graphics etc. and two other pictures i use as mask for my detection collisions. Each mask has only two colors, white and black and i check each frame if a pixel of the car collide with a black pixel of the masks.
This approach works of course but it's not really flexible. Whenever i want to change the look of a track, i have to redraw the mask and it's a real pain.
What is the general approach for this kind of game? How can i improve the flexibility of such a mask based approach?