The Train Connection

The op-ed has two completely separate metaphors about train tracks that are in-line with Rosen's background and recent experience:

“Meetings with him veer off topic and off the rails” (minor metaphor)

“The result is a two-track presidency.” (a major metaphor of the op-ed)

Rosen was on the board of directors of Amtrak and currently and previously worked for the Department of Transportation. 

Interestingly, in February 2018, Rosen criticized Chuck Schumer in reference to a train derailment (Daily Caller) (The Hill):

"Rosen specifically criticized Schumer’s December objection to Batory’s confirmation, which occurred in the immediate aftermath of the tragic Washington State Amtrak derailment that resulted in three dead, 70 injured, and cost over $40 million in repairs."

In the letter he also made some interesting comments about leadership which could be read as a dig at Trump:

“Any organization that has a strong leader at the top benefits from the leadership. I don’t think anybody can point to any organization that doesn’t benefit from a knowledgeable expert leading the organization in a capable way,” Rosen said.