Virginia Railway Express
The Cross Honor agreement between VRE and MARC offers free transfers, permitting passengers from each to travel on the other's reverse-flow trains (trains that are going in the opposite direction of the rush-hour commuters.)
Note: MARC will not accept free ride certificates or other promotional tickets. Cross-honor tickets not accepted on Amtrak trains.
Leaving Washington: On any VRE or MARC train leaving Washington until noon.
Returning to Washington: On any VRE or MARC train returning to Washington the same day.
Below is a basic example of how a person can utilize the benefit:
You live in Manassas, VA and commute in the mornings to New Carrollton, MD and return home in the afternoon/evenings. You would only need a valid VRE ticket (zones 6-1), displaying it both on the VRE and MARC trains to commute back and forth. You could not use a VRE ticket to go to New Carrollton in the evenings (after 12pm).
The reverse of this, if you were a New Carrollton resident wanting to commute to Manassas in the mornings and return home in the evenings, you would only need the appropriate MARC ticket to commute back and forth. At present, it would not be possible to do this if the destination is on the Fredericksburg line, as there are no reverse flow trains.