To be fair, you should be positioned at the end of the platform. If you are on the southbound platform, your should be on the north end of the platform. This means that trains approaching on the track in front, are not yet obstructed by the platformed and those on the other track do not have the platform to obstruct. This is the problem with New Carrolton, the platform is center, so half the trains have the obstruction of the platform.
An example of being obstructed.
being at the end of the platform, I could get it after it left the station. This in not always acceptable.
This is the situation at New Carrolton. It is center platform, the platform is used for both tracks in both directions. I still got some decent Videos.