Nearly seven years after Congress instructed the nation’s railroads to install an automatic speed control system by the end of 2015, the crash of a speeding Amtrak train last week has laid bare the industry hurdles, regional rivalries and often dismal economics of rail safety.

Miles of track on Southern California’s commuter lines still lack the system years after a 2008 crash killed 25 people there, fueling the drive to install the technology, known as positive train control. Chicago’s commuter rails are not likely to have the safety system for years, while comparatively sleepy train service on Amtrak’s Michigan line already has it.

And with most railroads expected to miss the congressional deadline, lawmakers in Washington are now fighting — not over whether to extend the deadline, but over for how long.

Senator John Thune of South Dakota and Senator Roy Blunt of Missouri have been the prime Republican backers of a bill that would extend the deadline by five years. The Senate commerce committee passed it this year.