To improve safety - particularly for the thousands of transit riders who pass through the square - the City of Boston's Transportation Department is proposing to close the wide right-turn slip lane in front of the Mattapan trolley terminal, widen sidewalks to reduce crosswalk distances, and add a new crosswalk across the Blue Hills Parkway to provide more direct access to the T station and the Neponset Greenway from the neighborhoods to the west.