Rail giant BNSF Railway was Berkshire Hathaway's biggest purchase ever in 2010 at $34 billion, and is currently the largest entity in its portfolio to date. So is there a lot of pressure to perform when you're reporting to Warren Buffett himself?

BNSF Executive Chairman Matthew Rose doesn't think so. He calls the acquisition a "marriage" that's going great.

"I told my team when we first did this that it'll take us 10 years to review this, and then we'll look back and say, 'Were we a better company in this structure versus being a publicly traded company?'" Rose asked. "And I think the answer will be yes."

Since Buffett bought the company, BNSF's total revenue has grown from $14 billion to $23 billion in just five years, an increase of roughly 64 percent. In addition, the company plans to spend $6 billion—a record level—in maintaining and expanding its 32,500-mile rail network this year.

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The U.S. freight rail industry is doing well across the board. According to the Association of American Railroads (AAR), it hauls nearly $70 billion worth of goods and commodities, and every freight rail job sustains another 4.5 jobs elsewhere.

Touching the American consumer and labor market gives the industry, and in particular BNSF—the second-largest freight rail network in the country—a great vantage point of the U.S. economy.

Earlier this week, data showed the U.S. economy all but flatlined in the first three months of 2015. Rose wasn't fazed by the weak first quarter, describing the overall economy as fine but not great.

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"I think we're in a weird transition. The oil and energy renaissance had such a spillover effect. It was creating a little bit of heat out there in terms of inflationary things," Rose said. "People were buying Ford pickup trucks, buying houses, doing house re-dos and everything else."

Fast forward a bit, and falling oil and gas prices "should [come] back into the consumer's pocket. We're in that transition where we really haven't seen that consumer take those savings and apply them to consumption," he added.

In his 2014 annual letter, Buffett referred to BNSF as Berkshire Hathaway's "most important noninsurance subsidiary," but added that BNSF had "disappointed many of its customers" with some service failures.

Rose, however, says a huge focus for the company is safety. In light of a BNSF oil train derailment in Illinois two months ago and new federal rules on rail tank car safety, he said the company will be reviewing its safety standards. It also plans to experiment with the use of drones to aid in track maintenance and bridge inspections.

However, he assured that railroads are inherently safe and that BNSF has a great safety record. Currently, it has the lowest incidence rate of employee injury per 200,000 employee hours, compared to the rail transportation industry as a whole.

Furthermore, safety has improved across the entire freight rail sector. The AAR reports the train accident rate fell by 46 percent, the rail employee injury rate dropped by 47 percent and the grade crossing collision rate declined by 35 percent since 2000.

"At the end of the day, we get the commitment that we make with communities," said Rose. "If we operate through your community, we have to operate safely. That's our commitment that we'll continue to live by."

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