single-vehicle accident; single-vehicle collision
Refers to a traffic accident involving only one vehicle, without another party.
昨夜、高速道路で単独事故が発生した。
A single-vehicle accident occurred on the expressway last night.
単独事故の原因は運転手の居眠り運転だった。
The cause of the single-vehicle collision was the driver falling asleep at the wheel.