The height of outdoor signs varies depending on the location and the visibility requirements. Generally, they should be visible to pedestrians and drivers from a safe distance. In urban areas, signs are often placed at a height of 4 to 6 feet (1.2 to 1.8 meters) above the ground. On highways, signs may be higher, around 10 to 12 feet (3 to 3.7 meters) to ensure they are visible to drivers traveling at high speeds.