When a claimant settles with an auto insurance company does that prevent civil law suit?
There are typically two kinds of claims that may arise from an auto accident: these are claims for (a) property damage; and (b) personal injury damage. It is possible to settle the "property damage" claim separately with the auto insurer of the other driver. If a claimant does this, then usually the claimant may still pursue the personal injury claims in a civil lawsuit.
However, when a claim is settled, there is typically a "release" given to the insurance company and signed by the claimant; and this release must specifically say that it is limited to property damage. This is general information and not legal advice. These situations are highly dependent on specific state laws, so you must consult an attorney in your area for advice on this topic.
Some states, like California, have laws that protect consumers/claimants and require release agreements to contain specific language if they are intended to be a "complete" or "general" release of all claims. If a "general release of all claims" is signed, it would usually prevent a later civil lawsuit for damages arising from the same accident or circumstances. So you can see that specific state laws and the "release" document that a claimant signs are critical to answering your question.