The so-called positive train control already is functioning on some trains on Metrolink's 91 Line, which goes through the San Gabriel Valley to Riverside.
Next week, the control system will be operating on some commuter trains on the San Bernardino Line, which runs from Union Station in downtown Los Angeles to San Bernardino.
As required by federal transportation rules, the safety measures are scheduled to be added to all the tracks and trains in the Metrolink system by the end of the year.
The measures, using global positioning and complex telecommunication systems, allows a train to be slowed to a safe speed as it approaches a curve in case the engineer has not applied the brakes and can stop a train if it runs a red signal, Metrolink spokesman Jeff Lustgarten said.
But as it now functions, positive train control would not have helped in Tuesday's accident in Oxnard in which a Metrolink train derailed after striking a pickup truck on the tracks, he said.
The sophisticated system can prevent train collisions such as Metrolink's 2008 head-on wreck with a freight train in Chatsworth that killed 25 people. That collision was blamed on a Metrolink engineer who was texting and failed to stop for a red signal
Shawn Nelson, the Orange County supervisor who is chairman of the Metrolink governing board, described the expansion of the positive train control system as "a huge step" toward keeping riders and residents along the tracks safe.
It will cost about $216 million in federal, state and local funding for the new controls to be installed on all trains operating on Metrolink's 512 miles of routes throughout six counties in Southern California.
Lustgarten said Metrolink is well ahead of other regional commuter passenger systems around the country in meeting the deadlines.