If you touch someone while driving you go flying.
And if you touch someone while flying, at least one of you will almost definitely spiral out of control.
Then again, we're already used to dealing with crazy collisions that knock us off the track; it's easier to recover when your vehicle is
supposed to be in the air.
There would need to be a lot of checkpoints to prevent shortcuts, and they should be pretty big so it wouldn't be a disaster every time multiple people went through the same part of the track at the same time.
If the track was big and wide enough (vertically as well as horizontally; opportunities to dive, gain a lot of speed, then either slow yourself down or risk crashing by maintaining that speed through an obstacle-filled straight), it could be pretty awesome.