Its not the county that you will have to sue, although conctacting the county or city where it happened won't hurt. It would be whatever company they contract out to do the roadwork that would need to be sued. Contact a lawyer. If there are signs marking that there is road construction, then you're basically out of luck. All it takes is a single sign showing that there is road construction in the area that the incident occured and you will be out of luck. Road construction companies cover their asses quite well. Be prepared for a fight. The cost of suing the road construction company may far exceed the cost of repairs. Make calls; it can't hurt.