As detailed here
For Public Multiplayer, the amount of cars that can run on a server now depends on the safety related restrictions that are set up. Unrestricted servers now start with 10 slots, and gradually increase with a simple formula: Slots = (Safety Rating) / 4 + (Track Medals)
In other words, each Track Medal is worth a slot (yes please use them) and the SA rating gradually unlocks more and more slots - at fairly low 45 SA we will find the break even to the 24 slots we are used to. Going beyond, 70+ SA will unlock the new maximum of 30 car slots.
