"The paramedic has to interact with someone who has zero interest in their roleplay and the person behind the wheel doesn't care for what the paramedic is doing and is going to roleplay as little as possible."
It is exactly what you said right there. What happens IG should be RPed. If you crash at 20 MPH you won't be very hurt, mostly shaken and probably a good bit disturbed. No need to RP severe injuries. But it should still properly be roleplayed. If one or multiple person/people saw the RP happen and they want to be RPing it then so be it. The rules clearly state you're only allowed to void if ALL involved parties agree to it, or an administrator makes a decision voiding RP.