In most cases, a lawsuit is filed in the county where the auto/motorcycle/truck accident occurred. But it does not HAVE to be limited to that county.
A common example will bring this into focus. Let's say you and your significant other are on a leisurely motorcycle stroll and a driver of a company car, drunk while on the job, turns left in front of you (the most common cause of an injury to a motorcyclist, by the way) and seriously injures both of you. His employer's place of business is in Cuyahoga County, he lives in Summit County, and the collision occurred in Stark County, Ohio. So which county is the proper one for bringing a lawsuit?
Answer: you can bring a lawsuit in any one of those three counties. The legal term which governs where a lawsuit is brought is called venue. You've probably even use of part of that term on the TV news when a criminal defendant asks for a "change of venue."
Under Ohio venue rules, a lawsuit can be brought in the county where: (1) a defendant has its principal place of business, OR (2) the defendant resides, OR (3) the accident occurred. There is no pecking order or priority given to one location or another.
So, in the example above, the lawsuit can possibly be brought in Cuyahoga County since an employer can be liable for an employee who injures someone in the course and scope of his or her employment. It can also be brought in Summit County because the employee/drunk driver resides there. And, finally, it is also proper in Stark County because that's where the collision occurred.
The decision of the best place strategically to bring an Ohio auto or motorcycle accident claim depends upon many unique factors, and each county would have its plusses and minuses, all of which should be discussed with the client before a lawsuit is filed.