TORONTO — Freight trains in Canada could be running again within days after the government forced the country’s two major railroads into arbitration with their labor union Thursday, a move aimed at averting potentially dire economic consequences across the country and in the U.S. if the trains are sidelined for a long period.

The government’s action came more than 16 hours after Canadian National and CPKC locked out workers over a labor agreement impasse. Both railroads said they…