In arcade mode you can access a special section of the track in the Riveria stage. First, select Arcade Mode and choose either practice or championship.

When you reach the Riveria stage, take note of the final 90 degree turn in the track (just before the final straight). There would be 2 red cones. Knock both of them down. After you have knock them down, you will hear two distinct tones, saying that the hidden section of the track have been opened.

Turn the car around, then look carefully on the car's right. An entrance would've been open. Drive right through, and you will enter a special point stage, where you will need to drive your car around and knock cones down to gain points.

Points gathered will not have any effect on the gameplay, therefore it is just a fun little bonus.