Simplify the following text for a Grade 6 native English-speaking person.
Original: In August 1995 , the TTC suffered the deadliest subway accident in Canadian history known as the Russell Hill accident , on the Yonge-University-Spadina Line south of St. Clair West station .
Simplified: In August 1995 , the TTC had a really bad subway accident in what it calls the Russell Hill accident , on the Yonge-University-Spadina Line south of St. Clair West station .