Once you reach the split in the road for the Construction Yard level (in the Platinum tracks), turn right. Once you go cross with the other road twice, build your speed up to 50 MPH or so (higher is better). Once you see the beam, aim towards it and drive on the concrete that is currently the shell for the building. Turn left, but don't do it as soon as you land. Once you get close to the wall, turn left. You'll still be driving on the concrete, but you'll see a jump ahead leading you back to the main course. You'll jump a place or two in the pack.