Catchup mechanism basically means :
- The closer you are to first position, the slower you go
- The closer you are to last position, the faster you go
Such a mechanism was also in the other Rollcage games (could be toggled on/off). It modified your speed and grip.
In Grip, I know it modifies your speed for sure - but not that sure about grip (your ability to stay on-track)
It's present in a couple of other racing games as well.