有兩列，On Roadway 和Off Roadway；Off Roadway是NHTSA定義，指的是車跑出路後撞上樹牆。。。。

On Roadway 和Off Roadway；

 

Off Roadway是NHTSA定義，指的是車跑出路後撞上樹牆。。。。

A run-off-road (ROR) crash occurs when a vehicle in transit   leaves the road and collides with a

tree, a pole, other natural or artificial objects, or overturns on non-traversable terrain. This type of  crash  usually  involves  only  a  single  vehicle.

NHTSA有博士研究這東東

 

https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811500