 The north end has traffic signals for pedestrians to cross traffic lanes.The former Ninth Street ("Singing") Bridge was a primitive affair built rather low over the river, and whose creosote-treated wooden deck was fitted with strips of metal plates spaced a tire-track apart to prevent excessive wear.As the tires rolled along, these plates, embossed to provide traction, would give off a high humming note—a note that suddenly would rise by about a fifth as a vehicle crossed from south to north