Tragically, there are a huge number of news reports about traffic accidents. The journalist usually write about them like this.
. an accident involving a car or car or car and truck or pedestrian
. give the location
. the number of people injured or killed.
. sometimes where the people were taken.
So I think to describe a bad accident, you might write something like -
There was a car accident on the highway in which 2 people were injured.
In that format, the reader can make their own judgement about how serious the accident was.