Dash-cam footage is the only real way to substantiate your claims in the court of law. Forget witnesses. Hit and runs are very common and insurance companies notoriously specialize in denying claims. Two-way insurance coverage is very expensive and almost completely unavailable for vehicles over ten years old-the drivers can only get basic liability. Get into a minor or major accident and expect the other party to lie to the police or better yet, flee after rear-ending you. Since your insurance won't pay unless the offender is found and sued, you'll see dash-cam videos of post hit and run pursuits for plate numbers.