What's the point of controlled practice?
What's the point of controlled practice? It seems like a horribly inefficient use of the track. You'll have periods of absolutely empty track, periods where there's one or two cars on track (often towards the end of a session)... then at the beginning of a new round a HUGE surge of cars all jammed together trying to test, run back to the pits and make a quick change and hope that the session isn't over by the time they rush back to test out the change.
Just leave the track open practice, or have, perhaps two groups by car laptimes: slow and fast.
Example:
Group1: Mini + spec + whatever has a slower lap time
Group2: GT1, GT2 etc... faster lap times
Make it so that the groups are approximately the same size so the track is used evenly, and the cars are of similar speed.
OR (what I think is the best solution) just leave the track open practice.
Artificially grouping the cars by speed is no good because, even in groups with faster cars there will be people struggling with their setups, spinning out etc - it's not good to see a car spin out, get hit by a far faster car of the same class and cause a problem for both drivers. For the guys struggling with their setup, being forced to run with the really fast guys makes it difficult to dial in your own car when you're spending the whole time watching for and jumping out of the way of quicker approaching cars. For the fast guys it's frustrating when you're on a fast lap, the car ahead spins out, and you T-bone him, possibly breaking parts on either car in the process. Nobody wants to see this happen, but with the controlled practice, drivers are forced to run all at the same time, rather than use their judgment as to the most appropriate time to make their runs.