I found this on a review of GP and Top Race
Top Race uses completely different rules for these cards, allowing them to be played as "breakdowns" or "catchups." Suppose the red/blue switch is played and red is farther along the track than blue. If played as a breakdown, the red car is pulled to the side of the road. It doesn't move again until the blue car passes it. If played as a catchup, the blue car pulls alongside the red car (or moves as far forward as it can until it is blocked).
As you might imagine, these changes have a dramatic effect on gameplay. Catchups are rare, since the odds of the right switch card getting dealt to the right owner are relatively small. But anyone can benefit from slowing down a leader, hence the popularity of the breakdowns. And with betting thrown into the mix, there's an added incentive to muck about with other cars.
I like this, and I think next time we play we can try these rules.