Major collisions between trains are not an everyday event in this country, but when they do happen, the results can be calamitous. Over the last quarter-century, Maryland has suffered two particularly horrific crashes, in Silver Spring in 1996 and Chase in 1987, in which a combined 27 people lost their lives. After each of these disasters, the question was raised: Isn't there a safer way to control trains?

It's a particularly vexing problem for the nation's increasingly congested 140,000 miles of rail lines, particularly on the approximately 25,000 miles where heavy freight trains share the rails with Amtrak and commuter trains. The danger of crew members failing to heed signals is substantial.

Investigators suspect that's what happened in the Sept. 12 commuter and freight train collision that killed 25 people in northern Los Angeles. While the exact cause of the crash is not yet known, it's possible the commuter train engineer may have been distracted by text messages on his cell phone.

Such an accident could have been avoided by technology known as Positive Train Control or PTC. This refers to various kinds of automated train control systems that can, for instance, make it virtually impossible to ignore a stop signal - the signal would essentially tell a computer onboard to hit the brakes.

Last week the House voted to require both passenger and freight operators to invest in PTC on certain routes by 2015. Whether or not the Senate agrees to these provisions, many in the rail industry doubt the timetable can be met. However well-intentioned, Congress is both a day late and a dollar short.

That's because a reliable and proven PTC system has not yet been developed. There are serious technical challenges to be overcome, and the major freight carriers are, at best, only now testing the technologies - and strikingly different versions of PTC at that. The cost could run into the billions of dollars.

This seems lost on Washington, which despite neglecting the nation's railroads for decades can somehow be suddenly surprised by the system's shortcomings. If the federal government were serious about improving rail safety, Congress should have invested more than the token $50 million grant program included in the proposal. It's a bit like leaving both the cost and details of air traffic safety up to individual airlines despite 9/11.

Train travel is still safer than riding in a car. But if passenger rail is to be more fully developed in this country - and the prospects of worsening energy and greenhouse gas woes necessitate such a move - then better train control systems must be developed. If the measure goes nowhere, at least it has brought greater attention to the need for PTC.