OMAHA, Neb. (AP) — Canadian Pacific has asked federal regulators to approve the structure of its roughly $30 billion proposed takeover of Norfolk Southern railroad.

The two railroads haven’t agreed on a deal, but Canadian Pacific is trying to address Norfolk Southern’s concerns about the U.S. Surface Transportation Board.

It’s difficult to predict how the board would handle a major railroad merger because there haven’t been any since tough rules for them were adopted in 2001.

Canadian Pacific CEO Hunter Harrison said Wednesday he hopes the board will offer investors a clear view of how it views the proposed voting trust structure for the deal.

Norfolk Southern shareholders will vote at their annual meeting whether they want the two railroads to discuss merging.

Canadian Pacific reportedly approached CSX railroad about a possible merger earlier this year while it continued to pursue its proposed takeover of rival Norfolk Southern. The latest overture to the Jacksonville, Florida, railroad was first reported by The Wall Street Journal. Canadian Pacific first contacted CSX in the fall of 2014 about a potential deal and was rejected.

Canadian Pacific CEO Hunter Harrison said his railroad remains committed to its roughly $30 billion bid for Norfolk Southern, which is based in Norfolk, Virginia.

But Harrison says he sees significant potential benefits in a deal with either Norfolk Southern or CSX, which both operate in the eastern United States. Canadian Pacific spokesman Martin Cej said that statement is accurate.

Officials with CSX and Norfolk Southern railroads both declined to comment.