As in many digital places, in Paragon City, you click on doors to go through them. City of Heroes has an unusual mechanic in that it is [click to open the door and walk through it] rather than [click to open the door] and [walk through the open door]. Okay, quarter-second saved per door by combining the two, yay? Well, no: you cannot do just the second half, so if the door is open, you usually must wait for it to close so you can [click to open the door and walk through it] rather than just [walk through the open door].
This becomes notable in task forces and other full-team affairs when everyone needs to go through the same door, particularly if the door open/close animation is long. With the addition of the Weekly Strike Target, this compounds as multiple groups might be using that door. The Statesman Task Force has three missions using the same submarine door. There is a constant traffic jam around that little circle.