By February, Highland Avenue runs between two gray walls and Central Hill is carrying more snow than anyone has room for. Snow Removal Somerville MA works that shortage of space for a living: plowing driveways, blowing out the tight spots, shoveling steps and walkways, and putting down salt where refreeze turns a sidewalk into a hazard by four in the afternoon. In a city built this close together, the difference between a passable driveway and an impossible one is a few feet of clearance and somebody willing to be out at five in the morning. Storms here arrive fast off the water and change to sleet without warning, so the return trip matters as much as the first pass. What people want is simple — a clear way out, before the day starts.