Unfortunately both AI Safety Car and a driven Safety Car don´t work properly in rFactor.
The AI Safety Car would probably be the better option, but it needs to be prepared for each track (it drives depending on the AIW) to make sure we don´t get things like in early 2010 where the Safety Car slowed down on the straights massively sometimes and drivers crashed into it.
A person driven Safety Car was used in an FSR CTDP Showrace after 2008 and it caused a lot of other trouble, as rFactor doesn´t know there is a Safety Car out drivers got Penalties for ignoring Blue Flags, which the Race Director couldn´t see, and the communication between the Race Director and Teams/Drivers can never be efficient enough to ensure the lapped drivers unlap themself by overtaking the Safety Car.
Maybe rFactor2 will offer better possibilities to run a Safety Car but in rFactor it´s not an option.