After a Metrolink passenger train with an engineer text-messaging at the controls slammed into a freight train in Los Angeles in 2008, killing 25 people and injuring 135, Congress finally passed a law ordering railroads to install systems that could automatically slow or stop trains in dangerous situations.

Safety advocates had been pushing the technology, known as positive train control, for two decades with few takers on Capitol Hill or among railroads. But the horrific accident — and the fact that equipment existed to prevent such carnage — led lawmakers to enact the Rail Safety Improvement Act of 2008, which mandated positive train control systems by the end of this year on about 60,000 miles of rail lines that carry passengers or hazardous materials.

That was an ambitious deadline for installing the technology, which uses global positioning satellites, sensors on engines and alongside tracks, and computers to monitor and take control of a train if the crew ignores signals or speed limits. And now it’s clear that the vast majority of railroads will not meet it.

This is not a surprise. The Government Accountability Office warned in 2013 that most railroads were behind schedule on installation. (The rare exception is Metrolink, which now has the technology in operation on its own tracks and trains, and is close to completing installation on tracks it shares with freight rail lines.)

Although safety advocates complain that railroads were too slow to start work, there’s no question that railroads have struggled with the complexity of designing and installing sophisticated systems capable of working across privately owned rail lines.

Some railroads have threatened to halt service rather than face fines and liability for operating without positive train control beyond the deadline. A widespread disruption could be devastating to the economy, considering that 40 percent of intercity freight traffic moves by rail. The Senate passed a bill earlier this year to postpone the deadline, and on Wednesday the House introduced its version, which would push the deadline to the end of 2018 and allow two additional one-year extensions on a case-by-case basis.

Nevertheless, there is understandable concern among railroads and their customers that Congress will dither and delay action until the last possible minute, despite bipartisan agreement on the need for an extension. Rather than risk a shutdown of crucial transportation services, Congress ought to fast-track a solution.

Yet a reprieve shouldn’t be an excuse to slow progress toward installing this vital safety technology. The need for positive train control was demonstrated again in May, when the derailment of a speeding train near Philadelphia killed eight passengers and injured 200. Any extension should include milestones, progress reports and scrutiny by railroad regulators to ensure positive train control is a reality sooner rather than later.

Editorial by the Los Angeles Times