Select the Salvage Wasteland track on quick race mode. Once the race starts,
go through the starting line, but stop immediately after it. Turn around and
face the part of the wall that looks different than the sheet metal. Drive 
through this section of wall, and follow the power line poles until you reach
a hidden track. The track is shaped like a big rectangle. On one section of 
pavement, there is a set of ramps.