The VRE Manassas Line is the shorter VRE Line, and shorter than any of the three MARC Commuter Rail Lines too. Trains operate 35 miles from Broad Run, a Park and Ride station just beyond Manassas to Washington-DC Union Station. The line opened on June 22, 1992 with trains stopping at the same ten stations they do today. The entirety of the line, except for the very short stretch of track onto the siding the Broad Run/Airport station (with this track continuing to the line's train storage yard) is shared with Amtrak's twice daily Northeast Regional trains to Roanoke along with the daily long-distance Crescent, and triweekly Cardinal.

Unlike the (longer and busier) Fredericksburg Line, the Manassas Line has minimal reverse peak service. The first inbound train of the AM rush hour, returns to Broad Run to become the last inbound train of the same rush hour. In the PM rush hour, there are two reverse-peak train. The work half-day train leaves Washington at 1:15pm, arrives at Broad Run at 2:34pm before turning from 3:38pm to 4:57pm. The next early rush hour train leaves Washington at 3:20pm, arriving at Broad Run at 4:39pm, returning at 5:10pm. In between these trainsets making round-trips, there are 5 trainsets that make only one round-trip per day, leading to 6 trains into Washington, DC during the AM rush hour, a midday 1:15pm returning trip, and 6 trains returning to Broad Run between 3:20pm and 7:00pm.

The intermediate stops (except Downtown Manassas and Alexandria, that are shared with Amtrak) only have platforms along one track this means that reverse-peak rush hour trains run express only stopping at Downtown Manassas and Alexandria, with the exception of the 3:38pm reverse-peak trip also stopping at Manassas Park and Burke Center because its early enough in the rush hour that its able to be scheduled around the next train returning to Manassas.

Like the Fredericksburg Line, the parts of the line closest to DC were originally identified as locations for potential Metro Expansions following existing rail alignments. The Backlick Road station site parking lot was originally purchased by Metro as a potential terminal station for Springfield (for a separate on stop Blue Line branch, with another one stop branch to Franconia). The operational headaches of having two separate one-stop branches resulted in this plan being abandoned in the late 1970s.

The ride on the Manassas Line is slightly less scenic than the Fredericksburg Line with the scenery being mainly rolling hills and trees. Historic Downtown Manassas is definitely worth a visit with lots of historic buildings. The day I did the Manassas Line it was a First Friday's festival with literally a sign for the edge of a Designated Refreshment Area (those of age can drink alcoholic beverages in the street) in the middle of the train platform at Manassas. I had a hard time finding a place to have dinner that wasn't super crowded as I train spotted the Crescent, and took the evening Northeast Regional back to Alexandria where I was staying.

All the other stations (except for Backlick Road that's more urban with a strip mall across the street) are in the middle of suburbia, although Manassas Park is trying to build a little town center (with a new city hall) around its station. The fact that the Manassas Line has reverse peak service makes riding it an easy way to experience VRE (including the front window of the Gallery cars in the Washington, DC-bound direction). The afternoon schedule even makes an easy weekday afternoon trip to explore Downtown Manassas a little.