Railroads have a storied history of trying to discourage passenger service in order to clear the tracks for profitable freight, and so perhaps Minnesotans can be forgiven for any suspicions about this winter’s chronic delays on the Northstar line. “Freight interference” has prevented commuter trains from operating reliably between Minneapolis and the northwest suburbs to the point that the fledgling Northstar service seems in jeopardy.

Unsure about railroad motives, state House Transportation Finance Committee Chairman Frank Hornstein called a legislative hearing last week to look into the delays and was left unconvinced that cold weather has been totally to blame. If delays continue as the weather improves, Hornstein says he won’t hesitate to investigate further. That’s the proper course.

It’s not just the Burlington Northern Santa Fe (BNSF), on whose tracks Northstar runs, that’s causing problems for transit, but a small freight railroad, the Twin Cities & Western, which, despite Hennepin County’s ownership of the tracks in question, seems to be standing in the way of another big project — the proposed Southwest light-rail line. Added together, the metro region is getting a strong message about freight’s priority over people.

It’s hardly a new problem, or a local one. The American Public Transportation Association has followed many freight-commuter conflicts over the years from California to Virginia. Solutions require recognition by the railroads that freight and passengers should peacefully coexist in the public interest — as they once did. Both sides of the rail market are on the upswing, after all.

As for the reliability problems affecting Northstar (and Amtrak’s Chicago-Seattle Empire Builder), BNSF’s three-part explanation is admirably straightforward:

• Extreme cold can cause a freight train’s air-pressurized brake system to fail. If brakes fail on just one car, the whole train stops and delays cascade throughout the system.

• The best way to prevent brake failure is to run more trains with fewer cars. In the frigid Fargo-Staples-Minneapolis corridor, trains are often shortened from 7,500 feet to 4,000, effectively doubling the number of trains.

• That puts extraordinary strain on a corridor that’s already experiencing a surge in freight traffic — more farm commodities, more cargo containers, more oil from North Dakota’s Bakken fields. Since Northstar began running in 2009, freight traffic on the corridor has increased by roughly 50 percent, from an average of 30 trains every 18 hours to 45.

Considering all of the headaches that extreme cold adds (frozen switches, icy roads preventing crews from getting to trouble spots and 20-minute restrictions on crews working outdoors), plus the uneven flow of wintertime freight traffic (heavy westbound early in the week, heavy eastbound late in the week), you begin to understand the small margin for error on the BNSF tracks and the difficulty of fitting Northstar trains into their slots on time. As BNSF Vice President Bob Lease points out, the conflict with commuter rail is almost unavoidable; the system is built for freight, which tolerates a degree of delay that commuters cannot abide.

All of that makes it clear the BNSF should consider expanding its Fargo-Staples-Minneapolis capacity. Extreme cold is a fact of life in Minnesota, and climate change suggests that extremes are likely to continue.

Unfortunately, BNSF’s $5 billion improvement budget for 2014 doesn’t include expanding capacity on the line in question, although the railroad does expect improvements in 2015. Of special interest is fixing the bottleneck created by a 9.5-mile single track between Xcel Energy’s giant coal-fired power plant at Becker and Northstar’s terminus at Big Lake. The point is that trains, whether hauling freight or passengers, need additional room to operate along one of BNSF’s most demanding and challenging corridors.