LOS ANGELES (Reuters) -A U.S. railroad industry plan to rely more heavily on technology instead of humans to conduct routine track safety inspections has drawn a backlash from labor groups and lawmakers who voiced worry that automated inspections will result in more accidents.

The dispute reflects simmering tensions in the global transport industry over the rise of automation. Also, U.S. President Donald Trump wants to slash regulations he says are holding back economic growth.

The Association of American Railroads (AAR) in April requested a waiver from the Federal Railroad Administration (FRA) that would allow freight railroads that use automation to slash the frequency of human-conducted track inspections by 75%.

If approved, the waiver would allow operators employing a so-called "track geometry measurement system" (TGMS), which can be attached to rail cars and spot derailment risks like tracks that are warped or too far apart, to cut human inspections to twice per month from twice per week.

The waiver would also provide railroads up to 72 hours to address defects, while human inspectors can immediately make repairs or choose to slow or stop trains.

The association, along with manufacturing and agriculture trade groups that back the proposal, say the change would result in earlier detection and remediation of track defects.

Tony Cardwell, president of the Brotherhood of Maintenance of Way Employees Division (BMWED) union that represents track inspectors and other rail workers, called AAR's analysis flawed.

The technology only checks about a quarter of the items in track defect inspections, he said. Human inspectors also see foundation issues like broken rail ties or water damage earlier, allowing problems to be fixed before they get serious enough for the technology to flag them.

"Track geometry is the end result of a defect, not the cause of a defect," Cardwell said.

Opponents of the plan have noted that after three train passengers died following a 2021 Amtrak derailment, a government report concluded that automated track inspections do not find as many types of track hazards as human inspectors.

A dozen Democratic U.S. Senators and the Democratic ranking members of the House Committee on Transportation and Infrastructure also called on FRA to deny the waiver in recent public comments on the proposal.

Kansas Governor Laura Kelly, who has more than 4,000 miles of railroads in her state, said automated track inspections "should not cut human track inspection at the expense of putting public safety at risk."

Republican lawmakers did not submit public comments.

The AAR said the waiver would actually improve railroad safety and operational efficiency.

"Layering technology on top of redundant and unnecessary, old ways of conducting inspections is not a way to make an industry competitive," said Michael Rush, AAR's senior vice president for safety and operations.

AAR member railroads, including megamerger hopefuls Union Pacific and Norfolk Southern as well as Berkshire Hathaway-owned BNSF, back the request.

The National Association of Manufacturers and the National Grain and Feed Association, both representing major U.S. freight rail customers, also support the proposal.

The decision is now in the hands of FRA, which does not face a deadline.

Train derailment rates are down over the last two decades, though there are still roughly three per day in the country, according to AAR and federal safety data.

Some have been major.

The village of East Palestine, Ohio is undertaking a billion-dollar environmental cleanup after a Norfolk Southern derailment in 2023. Two years earlier in 2021, an Amtrak derailment on a freight rail track in Montana killed three passengers.

After the Amtrak derailment, a National Transportation Safety Board (NTSB) report spelled out some of the limitations of TGMS technology. The report said the technology can provide detailed information on specific track parameters, but does "not capture the diverse array of unique track hazards detectable to human inspectors."

NTSB and FRA did not immediately comment.

(Reporting by Lisa Baertlein in Los Angeles)