Freight trains carrying crude oil shipments are blocking Amtrak trains in the northwest United States, according to complaints from the National Association of Railroad Passengers (NARP).

The passenger railway advocacy group wrote in a letter to Transportation Secretary Anthony Foxx that oil-by-rail shipments are blocking trains on Amtrak’s Empire Builder route, which runs from Chicago to Portland and Seattle.

Crude oil train shipments have come under fire after a series of derailments. The railroad passenger association said trains that stay on the tracks are also causing problems for Amtrak passengers.

“Delays of up to eight to ten hours have plagued the Empire Builder, inflicting extreme inconvenience—often at considerable personal expense—to literally thousands of Amtrak passengers and their families,” NARP President Ross Capon wrote to Foxx.

“While severe weather has played a contributing factor, the delays are in large part due to the logjam of rail congestion caused by hundreds of additional freight trains transporting crude oil extracted in North Dakota to refineries in other parts of the U.S.,” Capon continued.

Capon said NARP “recognizes the key role that America’s freight railroads play in fueling economic activity in the U.S.”

But he said that Amtrak and the freight rail company that operates the tracks the Empire Builder line runs on should be able to work out a better scheduling agreement.

“Amtrak and host railroad BNSF Railway Company must come together to ensure that the Empire Builder’s passengers have continued access to adequate, reliable public transportation,” he said. “The Empire Builder serves communities in Illinois, Wisconsin, Minnesota, North Dakota, Montana, Idaho, Washington State, and Oregon, with some 18.8 million people living within 25 miles of an Empire Builder station. The train acts as a vital transportation link for hundreds of rural communities to essential services in urban population centers.”

Supporters of the Keystone XL pipeline have said there would be less crude oil shipment by rail if the controversial project was allowed to be built. The Obama administration has resisted calls for constructing the pipeline, citing environmental concerns, even as it plans to ramp up its regulation of oil trains.

Capon said it was particularly important for officials to figure out a way to make service reliable on Amtrak’s northwest line because it travels through several smaller states that have sparse air service.

“Amtrak’s Empire Builder carried 536,400 passengers in fiscal year 2013 along a 2,256 mile corridor that has little in the way of transportation alternatives, and regularly experiences extreme winter weather conditions that close down airports and road networks,” he said. “Without a fully functioning rail service, many of these Americans will be effectively stranded.”

Amtrak spokesman Marc Magliari told The Hill that the company is dealing with the oil train-induced delays by shipping stations in Grand Forks, Devil Lake, Rugby, N.D. to make up time on its overnight cross country trip.

Magliari said Amtrak was negotiating with BNSF Railway for an equitable solution.

“We met two weeks ago with BNSF,” he said. “This dates back well before current winter weather blast. They told us they are making capacity improvements, but we should not expect to see an improvement in how our trains managed with their tracks until later this year.”

Magliari said the detours around trains that are carrying crude oil “requires passengers to disembark in Fargo, N.D. at 3:35 a.m. to get on chartered buses to take them to the three missing stops.

“We’re going to keep working with BNSF to try to mitigate these delays and inform our passengers what’s going on, but we’re concerned about this for our passengers and for our business,” he said. “This is our most popular, by ridership, overnight route in the country. It’s going to celebrate 85th anniversary later this month.”

Amtrak acquired the Empire Builder route from a private rail company when it was created by Congress in 1971.

A BNSF spokeswoman told the Grand Forks Herald newspaper that it was “working” with Amtrak to find a solution to the delays.

The company blamed the train backup on winter weather in the midwest U.S.

“BNSF service is being impacted by extreme cold and winter weather conditions across the Midwest,” BNSF spokeswoman Amy McBeth told the North Dakota paper.

“The extreme cold and snow are presenting significant operating challenges for our operations,” McBeth continued. “To recover, we are operating our westbound trains on our route through New Rockford and eastbound traffic through our Devils Lake route. We will continue working with Amtrak as our network recovers.”