A merger would create a 52,000-mile system spanning the U.S. but would face regulatory obstacles. Combining Union Pacific and Norfolk Southern into the first transcontinental railroad in the U.S. would create a 52,215-mile colossus that could offer seamless service from coast to coast, bypassing longtime interchange choke points in Chicago and at gateways along the Mississippi River. The two railroads confirmed today that they are in advanced merger discussions. The talks, they said, may not result in a deal. Plus, there’s the potential for a bidding war if BNSF Railway, UP’s Western rival, decides to make a move for NS....