Watch Your Speed Walking at the Haymarket T Station

On the outbound platform for the Green line (the line going on to North Station and Lechmere) there an electronic sign used on street and highways that shows “Your Speed” and “Speed Limit”.

Now what in the world is a speed sign doing at a platform where Green line cars stop? I asked a friendly T-employee at the entrance why it’s there, “I don’t know,” she said, smiling. “It’s just there.”

Only can think it’s an MIT student prank. Or, maybe it shows how fast passengers run to get out of the station, where the roof leaks.  (It is placed in front of an MBTA super modern, state of the art, subway station AC unit, known colloquially as a fan.)