You file suit.
There are other things you can do, depending on how much money you want to spend.
You can get a reconstruction of the accident performed by an engineer. You can request the data recorder from the truck and from your own car – if they exist, and can be located. (Not all trucks have them.)
You can check with your own insurance company, to see if the truck company has made a claim for the damage they sustained because of the accident. (If the truck’s insurer thinks the truck is at fault, they will pay your insurance company what it paid to fix or replace your car, and any deductible.)
You can try to get written statements from witnesses, and show them to the insurance company.
But chances are, nothing will do as much good, or work as fast, as filing a lawsuit.
Insurance companies pretty much do what their insured tell them to do, at least as long as it makes sense. If their own truck driver says it’s not his fault, they believe him. After all, they decided to start believing him when they took his application and decided to insure him.
If you want to change their mind, you have to show them that what their driver is saying does not make sense. And that a jury will punish him for lying.
And the best way to do this is to take his deposition, collect all the other evidence you can, and then throw it in their face. If he’s lying, they usually will figure it out.
I have been a lawyer over 30 years. If you have been injured in a truck accident in the Cincinnati, Ohio area, call me at 513-621-4775.
Because all situations are different, and because there may be other facts pertaining to your case that I don’t know about, you should not rely on this answer for legal advice. I am not your attorney, and no lawyer client relationship has been formed. All discussions are limited to Ohio law unless otherwise indicated. And past performance cannot be used to predict future results.