Also, if someone is on medications for seizures they have obviously had them before, and some people can sense one comming. It's a phase called aura where you will experiance a smell, visual or auditory sensation to give you a little warning to prepair for it. I'm not saying that colisions do not or cannot happen because of a seizure I am just saying that it chances are pretty slim. I am not sure but there are laws about driving if one is prone to seizures.
This is a "what if" statenment, but it still doesn't make it an accedent because there was a cause. The guy wouldn't walk out of his car after convulsing and say "opps had another seizure!"
Just like astma, ADD,diabeties, COPD, hearing loss,etc. it is a medical condition. There are may types of seizures but as far as epilepsi goes it is a condition.
Also with medication, they can offer/give the patient drugs that will eliminate the sezure within munites. So unless the person forgot to take his/her medication, or it is expired I think they would be fine.
You can suddenly have seizures but these people are usally taking a drug to prevent these but if they forget to or don't take them they will be prone to seizures. Anyone can have a sezure but there is usually some other factor involved. Already uncontious, drug overdose, poisioning, trauma. If your not already taking something for it.