Engineer Robert M. Sanchez pulled Metrolink 111 out of the Chatsworth station and was rolling north at 54 mph. About a mile later, he entered a restricted speed zone and throttled down to 42 mph.
Just ahead, on his right side, was a red light. It was a warning to stop so that an oncoming Union Pacific freight train could move off the main track and onto a siding. But Sanchez sped past the light and barreled over a switch mechanism that was supposed to guide the other train onto the side rail, according to federal investigators.
A quarter mile later, along a sharp curve in the tracks, the two trains collided at a combined speed of 83 mph. Sanchez never hit his brakes.
The job of sorting out what happened at 4:23 p.m. Sept. 12 now falls to a group of National Transportation Safety Board investigators led by Wayne Workman.
"It's about gathering facts and only facts," he said. "Our purpose is to investigate this and provide the best possible results."
Sanchez's actions are at the center of a federal investigation into the worst train accident in modern California history, which killed 25 people and injured 135.
Yet even as investigators uncover evidence suggesting Sanchez may have been responsible for the devastating collision, they are vowing to conduct a wide-ranging inquiry that will examine any number of possible causes and probably take a year to complete.
"The more narrow your investigation, the less clarity you have," Workman said.
He and other federal officials said in interviews this week that they plan to produce a detailed report that pinpoints a probable cause and lists recommendations to address factors contributing to the crash.
"It's a very deliberative, careful process," said agency board member Kitty Higgins, who responded from Washington, D.C., with the safety board's 17-member "Go Team."
The group, which includes rail experts, electrical engineers and psychologists, was on call when the Sept. 12 crash occurred and flew to Los Angeles the next morning.
Some of them, like Workman, are railroad veterans. The 59-year-old lead investigator is a fourth-generation railroad employee who started as an engineer and became a general manager of a rail company operating on the East Coast before joining the agency.
The NTSB is one of the smallest federal agencies in Washington. It has 400 employees, half of them dedicated to investigations. Typically, it investigates about 2,000 aviation accidents each year and about 500 other accidents on railways, highways and waterways.
The NTSB has no enforcement authority and relies largely on the thoroughness of its investigations and final reports. "The only thing the board has is its credibility," said James E. Hall, who chaired the agency's five-member board of directors during the Clinton administration.
According to the agency, 84% of its rail safety recommendations have been adopted by regulators and rail companies.
To leverage its limited resources, the agency relies on the "party system," which Workman and his investigators launched at the scene.
Every party involved in the Chatsworth collision -- Metrolink, the Los Angeles Fire Department and the union representing the Union Pacific engineer, among others -- has been asked to take part in the investigation.
Aiding them are experts from the Federal Railroad Administration and the California Public Utilities Commission, which shares some rail oversight with the federal government.
Investigative groups were formed, with one person picked as a coordinator to work with Workman throughout the process. The groups include a human performance team to study the actions of every rail employee involved in the crash. Other groups are examining warning signals on the tracks and reviewing the emergency response of hundreds of firefighters and law enforcement officers.
A crash-worthiness group is looking at the design of the passenger cars to determine whether structural flaws such as weak doors or interior tables hindered rescue efforts or contributed to fatalities.
"They will painstakingly figure out how every person was injured or died," said Barry Sweedler, who spent nearly 30 years with the agency as an investigator and administrator.
Workman and his team were scheduled to return to Washington today.
In the coming weeks, metallurgy experts will analyze pieces from the shattered Metrolink engine in the NTSB laboratory and analysts will write draft reports.
Among the chief tasks, investigators said, will be to pore over Sanchez's medical and training records to develop a profile of his behavior during the final days before the crash.
The safety board has said the engineer was sending and receiving text messages while on duty the day of the crash. What it did not say, however, is whether he was doing so as he left the Chatsworth station.
To the uninitiated eye, Sweedler said, the fact Sanchez failed to hit his brakes suggests he didn't see the oncoming freight train, perhaps because he was sending a text message.
But Sweedler cautioned against jumping to conclusions. "You think you have a smoking gun," he said, "then you get information that contradicts that the next day."
(BEGIN TEXT OF INFOBOX)
86 Metrolink riders hospitalized after the Sept. 12 crash
21 Riders hospitalized Friday
4 Riders in critical condition
2 Riders in serious condition
3 Riders in stable condition
12 Riders in fair or good condition
Source: Times research