These will unlock as you progress through the career story.
The first will come right after you have met Zack for the first time
The second will come a little after you have met Hector for the first time.
The third will come up just after the "Rollercoaster" mission.
You will have to complete some races after meeting hector and completing "Rollercoaster" to get them to appear. Unfortunatly I can not be preciese with the amounts of races. NOTE You dont have to visit them, just unlock them