Months after Washington approved billions to significantly expand Amtrak's footprint across the country, an early attempt at growth has reached an impasse in a test case that could define the American rail network for a generation.

The escalating clash is playing out on the Gulf Coast, where Amtrak wants to restore service 17 years after Hurricane Katrina flooded the region's rail infrastructure. Amid fanfare over federal money as a president nicknamed "Amtrak Joe" watches from the White House, the passenger rail and the freight railroads that control the tracks are in mediation to resolve disputes over Amtrak's proposed service levels.

At the core of the conflict is a mandate that requires freight railroads to give passenger trains access to rail track and preference over other rail traffic. A federal board is weighing the fate of Gulf Coast passenger service in a triallike process pitting Amtrak against freight railroads. Because Amtrak operates mostly on tracks owned by others, the case could set precedent as the passenger railroad embarks on a $75 billion expansion with bipartisan support.

"This is the bellwether case for the expansion of any passenger rail in this country," said John Robert Smith, chairman of the policy organization Transportation for America. "If the freights manage to kill this proposed service, it will send a chill through the rest of the nation aspiring for passenger rail."

Amtrak's plan for the 140-mile from New Orleans to Mobile, Ala., is one of 39 new routes the railroad is pursuing as part of its plan announced last year to reach dozens more cities and towns. The aspirations coincide with Washington's priorities for more rail and alternate modes of transportation, supported by the bipartisan infrastructure law President Joe Biden signed last year. The measure includes $66 billion for the nation's ailing rail network.

But any expansion in Amtrak's territory, which has remained nearly unchanged during its five decades, would boost pressure on freight companies and add trains to shared tracks at a time when the industry is under scrutiny over supply chain disruptions.

"We figured out the money piece," said Amtrak chief executive Stephen J. Gardner. "We've solved one-half of the problem, and now that puts sort of the spotlight on this relationship with the [host railroads] and how do we find a productive path forward."

Amtrak's federal aid lessens the financial barriers to launching new train service, abating Amtrak's biggest impediment to growth. Negotiating track access is the next hurdle.

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Outside its busy Northeast Corridor, Amtrak mostly operates on tracks owned by private railroads. Under federal law, it pays the companies to use the tracks -- a sum that, according to Amtrak, totaled $135 million last fiscal year. The arrangement dates to 1970, when Congress created Amtrak, relieving private railroads from their obligation at the time to provide intercity passenger rail service.

Fifty-two years later, tension continues to plague that tenant-owner relationship. Amtrak argues the railroads disregard preference for passenger trains, saying freight trains caused nearly 900,000 minutes of passenger delays last year. The freight industry has countered over the years that Amtrak oversteps its authority.

The two sides occasionally strike accords on service increases and new routes. Some agreements have been transformative, as in Virginia, where Amtrak and CSX partnered with the state last year on a $3.7 billion rail expansion.

But along the Gulf Coast, six years of talks have led nowhere. The Southern Rail Commission -- a panel of state-appointed members from Louisiana, Mississippi and Alabama -- has pushed for a decade to bring trains back, helping to secure $66 million for improvements. The federal government in 2015 convened a group to evaluate the restoration of service, bringing together railroads and the three states that would be served by the line.

Negotiations stalled as Amtrak introduced a service plan that was different than before Katrina, with more trains using the corridor during peak hours. The two sides couldn't agree on the capital investment needed to restore service: The Federal Railroad Administration estimated the price tag at $118 million, while CSX said it would take $440 million.

CSX, which owns most of the track between New Orleans and Mobile, said it wouldn't oppose Amtrak resuming pre-Katrina service, when long-distance trains arrived overnight, three times a week. But the company says more study is needed before Amtrak brings two daily round trips between the port cities, including stops in the Mississippi cities of Bay St. Louis, Gulfport, Biloxi and Pascagoula.

CSX said eight to 10 freight trains traverse the full route daily, while other local trains and mechanical equipment use stretches of the line. Officials with the Port of Mobile, the city of Mobile and Alabama have raised objections to Amtrak's proposal, citing possible effects to the port, which city leaders say moves more than 58 million tons of cargo annually.

But Amtrak calls the rail "a lightly used mainline" that is far less complicated than Amtrak's Washington-to-Boston tracks, which handle about 2,200 trains daily.

"Most of the route [in the Gulf Coast] is single track, but so is the vast majority of Amtrak's route network," Gardner said to the Surface Transportation Board (STB) in February. "Yes, it has drawbridges, but not as many per mile as Amtrak's Northeast Corridor in Connecticut. Yet somehow, we still accommodate 68 trains a day over that route."

Because the railroads have not agreed to give Amtrak access, federal statute tasks the STB, an independent federal agency that regulates freight rail, with determining whether more passenger trains would "impair unreasonably freight transportation."

The Biden administration has taken a prominent seat at pushing Amtrak's petition, saying a resolution along the Gulf Coast is key to the future development of intercity passenger rail across the nation. At stake, it says, is Americans' access to adequate transportation.

"Service delayed is service denied," Amit Bose, head of the Federal Railroad Administration, said in February while urging the panel to ensure the "railroads fulfill their fundamental statutory obligations to allow the expansion and improvement of intercity passenger rail services."

In a May letter to the STB, John E. Putnam, acting general counsel at the Transportation Department, said efforts such as restoring Gulf Coast rail passenger service are critical to the administration's transportation goals of "combating climate change, ensuring equity in personal mobility and driving economic growth and vitality."

"Unfortunately, despite an extended period of examination and the investment of significant funds, Amtrak has been unable to obtain the agreement of the host freight railroads, and there is no clear or imminent path to the restoration of this service, absent the Board's intercession," Putnam wrote.

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Support for Amtrak is widespread in Louisiana -- home to a terminus stop in New Orleans -- and across Mississippi, where four of the six stations would be located. Local officials tout the return of Amtrak as an economic asset to boost tourism and an alternative to traffic-clogged highways.

Alabama leaders, however, say their port, shippers and freight customers would suffer from disruptions to a tightly managed schedule of freight trains. Alabama House leader Mac McCutcheon (R) told the STB he is also concerned the state might have to foot the cost of Amtrak's passenger operations.

The office of Alabama Gov. Kay Ivey (R) did not respond to multiple requests for comment. Mobile Mayor Sandy Stimpson declined to comment for this story.

In testimony to the STB, Stimpson said it would be premature to grant Amtrak's petition without more study and infrastructure improvements, warning that "any action that stands in the way of the continued efficient and productive operation of the Port of Mobile must be treated with microscopic scrutiny."

The dispute has sent shock waves among rail advocates, where supporters of intercity train service and local leaders who want Amtrak in their communities fear the Gulf Coast dispute could translate into freight companies rejecting passenger rail proposals. Several mayors have made pleas before the board on Amtrak's behalf.

"People literally stop me on the street and tell me how excited they are that we might get passenger rail here in Madison," Satya Rhodes-Conway, mayor of the Wisconsin city, said in testimony to the board. "However, our ability to implement Amtrak service here would be imperiled by the precedent set in this decision."

In the meantime, Amtrak is still easing into other markets. Trains will return to Burlington, Vt., in July for the first time since 1953. Plans are advancing for more trains between Washington and Virginia's Norfolk and Roanoke areas using tracks owned by CSX and Norfolk Southern. Amtrak is also negotiating with Canadian Pacific to add service between Chicago, Milwaukee and the Minneapolis area.

But back on the Gulf Coast, the STB in June ordered mediation, eventually giving Amtrak, CSX and Norfolk Southern a month to reach a settlement after the process begins. The five-member panel has listened to more than 80 hours of sworn testimony, examination and cross examination since February. More hearings are expected this summer as the railroads file evidence by a July 13 deadline.

Board members have questioned the transparency of Amtrak and the railroads, while admonishing their lack of candor with each other.

"Part of me wants to say both sides should lose, but that's really not possible," Board Chairman Martin J. Oberman said in May. "I can't make you play nice, but I think it would be much more productive if you did."

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In Bay St. Louis, a city of white sand beaches an hour east of New Orleans, a century-old train depot across from shops and restaurants has been restored to include a Mardi Gras museum. Still missing are the passengers.

In 2005, Hurricane Katrina brought down homes and buildings, piers and the marina. As the city recovered, a new harbor and a $19 million sea wall were built a decade ago. Antique shops, art galleries and restaurants popped up in downtown. The train depot is now the visitor's welcome center and a space for city festivals and events.

"We built back better," said Nikki Moon, a longtime resident of Bay St. Louis, whose home and business were destroyed during Katrina. She said the city's comeback is missing an important piece: trains.

"Having this train would show that there is a lot for people to come and see, a lot for them to enjoy in the bay," said Moon, a retired innkeeper and regional tourism leader. "Amtrak coming in would be a game changer for our town and, I believe, for the entire coast."

Bay St. Louis, population about 10,000, relies heavily on tourism. Its small-town feel has been a draw for urbanites in the South, fueling growth during the coronavirus pandemic.

City officials say tourists arriving in cruise ships in New Orleans or Mobile could hop on a train to visit the Mississippi coast's beaches and casinos. Nondriving visitors, including the international tourists who come to New Orleans, would be able to plan a day trip or an overnight stay.

In a corridor where flying between New Orleans and Mobile requires a layover in Atlanta, transportation advocates say a three-hour train ride would be competitive with driving.

Amtrak's pre-Katrina service did not offer that choice during daylight hours. The route was so long -- from Florida to California -- that the train arrived in Mississippi during the overnight hours. Proponents say the shorter route during daylight would give roughly 2 million nearby residents an option to commute by train while offering more reliable and frequent service.

"When a train comes through in the middle of the night, three days a week, people don't really buy into it," said Kay Kell, a member of the Southern Rail Commission. "This is an area that has been unserved for quite a while, and we know a large population would use the train."

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Regardless of whether an agreement between Amtrak and freight railroads is reached through mediation, the board could deliver a verdict by the end of summer. Some railroad experts say the case highlights a growing hostility.

"Reasonable people should be able to come to an agreement," said Robert VanderClute, a private consultant who spent 26 years working at Amtrak. "Collaboration is critical, and we had it at one point. I don't know where it went astray."

Amtrak set up cameras along the route as hearings were carried out this spring, live-streaming empty tracks and birds singing in the background under the title "CSX's Very Busy Gulf Coast Corridor."

Days earlier, Amtrak had argued that freight companies wanted unreasonable investments from the passenger rail and for taxpayers to subsidize infrastructure for the benefit of their shareholders. CSX and Norfolk Southern leaders blasted Amtrak as trying to force itself onto their rails without consideration for the effects on freight customers.

The case is about more than a New Orleans-to-Mobile passenger route, CSX president and chief executive James M. Foote said at an STB hearing.

"It's about a new national agenda and Amtrak's desire to change the law and create a new road map, proposing new passenger service without working with most carriers or local communities to first add necessary capacity," he said.

Amtrak's Gardner said the case represents a turning point for American passenger rail. Amtrak's network today, he said, is smaller than in 1971, even as the nation added 120 million people.

"We need to serve more places, serve more people with more trains," he said. "We can't let -- as in the case of the Gulf Coast -- years and years go by where the public's will and where the federal government's investment is stymied."