There used to be a stop sign and a one way street indicator at the exit to the Porter Square Galleria parking lot onto White Street. Looks like the post is still there, but the stop sign has gone missing.

Here's the stop sign in place, captured by Google street view in Oct 2017.

Thank you for contacting us. Unfortunately the City cannot install signs or other traffic devices on private property. However, your request has been sent to the property owners.