by chucksc
Yes but always under the direction of the station agent who is supposed to know what traffic is about to take his station....
Half of VRE's station only have a single platform, so there would be no reason to cross. It is also prohibitively expensive to build bridges and tunnels at all of the stations especially the smaller ones. All of the stations on the Penn Line/NEC have crossing bridges/tunnels (including the low platform ones north of Baltimore) except Martin State Airport and Perryville which have single platforms.
Gaithersburg station actually does have a pedestrian bridge across the street to the parking garage, but of course only people who park in the garage (most MARC passengers) actually use it.