A single-vehicle collision or single-vehicle accident is a type of road traffic collision in which only one vehicle is involved. Included in this category are run-off-road collisions, collisions with fallen rocks or debris in the road, rollover crashes within the roadway, and collisions with animals.
The term single-vehicle collision is not generally used unless the rider or driver and passengers of the vehicle are the only ones injured. Crashes with only one motor-vehicle where bystanders (such as pedestrians or bicyclists) are injured are not typically called "single-vehicle," although technically the term does apply.
The normal inference is that the cause is operator error. Common factors contributing to single-vehicle collisions include excessive speed, driver fatigue and driving under the influence of alcohol or other drugs. Environmental and roadway factors can also contribute to single-vehicle crashes. These include inclement weather, poor drainage, narrow lanes and shoulders, insufficient curve banking and sharp curves. Some vehicles have unpredictable car handling characteristics or defects, which can increase the potential for a single-vehicle collision.
Suicide is also sometimes cited as a possible cause of single-vehicle collisions, although this is difficult to determine.