A driver makes an illegal U-turn by turning the vehicle around to go in the opposite direction where that maneuver is forbidden by traffic law, road signs, lane markings, or safety conditions.

Common examples include turning around at an intersection marked "No U-turn," crossing a double yellow line where it is not allowed, making the turn on a curve or near a hill where visibility is poor, or doing it in heavy traffic where other drivers cannot react safely. Even where a U-turn is not specifically banned by a sign, it can still be illegal if it is made unsafely or interferes with other traffic. A ticket for an illegal U-turn is usually treated as a moving violation because it involves how the vehicle was operated on the road.

In an injury case, an illegal U-turn can be strong evidence of negligence. These crashes often happen suddenly and can lead to side-impact collisions, motorcycle wrecks, or abrupt braking that causes neck, shoulder, or back injuries. Police reports, witness statements, dashcam video, and skid marks may help show whether the turn violated a rule or created an obvious hazard.

For a Maine claim, fault matters a lot. Maine follows modified comparative fault with a 50 percent bar, which means an injured person cannot recover damages if they are found 50 percent or more at fault. So if an illegal U-turn contributed to the crash, that traffic violation may directly affect who pays and how much can be recovered.