On Wednesday, Muni released video of the weekend accident. It's the first time we've seen exactly what happened, as the National Transportation Safety Board wrapped up its on-site investigation and some at City Hall call for a probe.
Federal investigators are leaning towards human error as the cause of Saturday's crash. They have ruled out anything mechanical and part of their review centered on the surveillance video, which was shot from several angles.
Muni video taken from several cameras on the West Portal station showed how a train got rear ended. In the upper right hand corner you see a small image of the headlights of the incoming train. It's sitting in the tunnel waiting for the signal to proceed.
According to the NTSB, it's at this point the train was switched from automatic to manual mode, which prevents the emergency brakes from kicking on.
Federal investigators say the driver told them he blacked out, and his train plowed into the other one injuring more than 40 people.
In the wake of the crash, Muni is reinforcing a rule that is on the books, but one union leader said is a long-standing practice, switching to manual without waiting for authorization.
"We're making hourly announcements to our operators and we've issued a bulletin and central control is monitoring it very closely to keep the system as safe as possible," said Muni Spokesperson Judson True.
Muni is not saying if the union's claims are true that management has known that key safety rule is often ignored to help drivers stay on time, but there are records that could shed light. The NTSB is examining them and City Hall also wants a look.
Some supervisors are now calling for hearings and for the controller to conduct an audit of Muni practices.
"There is data that will show on this day, on Saturday, how many other trains shifted from automatic to manual, we can look at all the records and what happens when central control is notified," said San Francisco Supervisor Bevan Dufty.
The NTSB has completed its on-site investigation, and said its post-accident examinations have not revealed any problems with the braking system or any other mechanical element of the train.
Federal authorities still need to review the driver's medical history, and have subpoenaed his cell phone records to see if that played any role in the collision.
The driver is still hospitalized.