(FORT GRATIOT TOWNSHIP) -- An 18-year old Fort Gratiot Township woman was injured in a single-vehicle crash Tuesday morning. St. Clair County Sheriff Tim Donnellon says the driver, Rachel Kolar was traveling east on North River Road near Parker Road around 8:45 a.m. when she lost control of the car on the snow covered roadway. The vehicle crossed three lanes of traffic, went sideways, and slammed into a 4" diameter steel mailbox post that was filled with cement. The passenger side door struck the post, causing the car to flip onto its top. Kolar was transported by Tri-Hospital EMS to Port Huron Hospital and later transferred to St. John's Hospital in Detroit with unknown injuries. The Michigan State Police and Fort Gratiot Fire and Rescue assisted at the scene. Sheriff Donnellon says that most mailbox posts would snap in a situation like this, but because of the reinforcement, this post did not. Donnellon is asking residents with that type of post, to replace it. He noted that the severity of the crash could have been lessened if the post was made of wood or some other material that would break away with severe impact. St. Clair County Road Managing Director Kirk Westson said there is no state law against having such a post in place, but there is a county policy that if one is discovered in the county right of way, it will be removed.