Some of the first roadside signs—ancient milestones—merely gave distance measures. Hazard warnings were rare though occasional specimens appeared, such as the specific warning about horse-drawn vehicles backing up which was carved in stone in Lisbon's Alfama neighborhood in 1686. The early signs did not have high-contrast lettering and their messages might have been easily overlooked. Signs were written in the local language (); symbolic signs, though long used on certain tradesmen's signs (like the pawnbrokers' tri-ball symbol) were to be used for traffic only much later in history.