The Surface Transportation Board said on Wednesday that Union Pacific and Norfolk Southern have formally filed a notice of intent to combine, triggering the U.S. regulatory review process for a proposed $85 billion merger between the two major railroads.

The merger would create the United States’ first coast-to-coast rail network, spanning 50,000 miles and 43 states.

Big mergers sometimes lead to big layoffs. Might that happen in the Harrisburg area — home to a giant Norfolk Southern hub — if Union Pacific completes its buyout of Norfolk Southern? Probably not, according to one industry expert.