They were on their own: that's what National Transportation Safety Board investigators say about two BART track workers who were killed in an accident last Saturday. 

During a briefing yesterday, NTSB lead investigator James Southworth told reporters the workers requested approval from the control center to go onto the tracks.

They received that approval but were supposed to be responsible for their own safety. 

BART rules required one of the workers stay off the tracks and act a lookout for the other.