The National Transportation Safety Board has completed its on-site work in the investigation into a crash involving two San Francisco Municipal Transportation Agency light rail vehicles on Saturday afternoon, according to NTSB Acting Chairman Mark V. Rosenker.
NTSB officials also released control of a video of the crash that had been provided to the safety board by the SFMTA from a surveillance camera mounted at the West Portal station where the crash occurred.
The video shows a K-Ingleside Line train coming to a stop inside the station, and then an L-Taraval train coming into the picture and striking the K train from behind while people on the platform jump back in surprise.
The crash, which happened at about 2:50 p.m. Saturday, injured 48 people including four who suffered serious injuries, according to Muni officials.
The initial investigation into the crash discovered that the operator of the L train, identified as Henry Gray, switched the train into manual mode 24 seconds before it crashed into the K train.
Muni trains are supposed to remain in automatic mode, not manual mode, when traveling through the station.
NTSB investigators are looking at human error as the likely cause of the crash, having found no indication of malfunctions in the braking system, emergency brake, or signal system.
Gray told an NTSB investigator that he “blacked out” as his train approached the platform. The NTSB will be reviewing the medical history of Gray, as well as any medical conditions or treatments that might have caused the crash.
While there is no indication that the use of a mobile phone played a role in the collision, the mobile phone records of Gray have been subpoenaed for review, a routine part of similar accident investigations, according to the NTSB.
The Los Angeles-based NTSB investigators have left San Francisco and will continue the investigation from Southern California.
Muni officials have implemented a number of guidelines aimed at increasing safety in the days following the crash.
As of this Monday, train operators will be written up if they are observed in manual, or cutout, mode without authorization from central control.
Additionally, if a train is seen moving in manual control without central control permission, the train controller will stop the train and contact its operator. Hourly announcements started Monday to remind operators that they must not go into manual mode or bypass any vehicle function, or change operating modes, without approval from central control.
Also on Monday, a bulletin was issued to light rail vehicle operators to remind them of existing rules and instructions regarding the changing of operating modes.
Supervisors at the Embarcadero, Church and Duboce and West Portal stations have also been alerted of the enforcement regarding the changing of operating modes.
“We have been working hard in recent years to improve the safety culture at the SFMTA and going forward we are redoubling those efforts,” SFMTA Executive Director Nathaniel P. Ford said in a statement.