Because it was describe an accident not emphasis on a road. So we use to say in an accident not "on" an accident, right? I hope you know what i mean. :")
...一台電動 Yesterday John met Peter on the road by accident. 昨天John 跟 Peter在路上不期而遇...
... the heart of a young woman, Denise Darvall, the victim of a road accident, to the body of Louis Washkansky, a dentist in his ...