What form of lead is typically used for highways?

The correct answer is yellow chromate, which is a form of lead often used in highway applications primarily due to its corrosion-resistant properties. Yellow chromate is not only effective at preventing rust on various structures, but it also promotes visibility, which is an essential safety feature for road signage and markings.

Highways require materials that can withstand environmental stresses, including exposure to traffic, weather, and chemical elements. Yellow chromate provides a durable finish that withstands these challenges and ensures that road markings remain visible, contributing to overall road safety.

In contrast, the other forms of lead mentioned do not typically serve the same purpose or offer the same benefits in a highway context. For instance, white lead has historical applications primarily in paints but is not suitable for outdoor use due to its instability when exposed to moisture and sunlight. Red lead serves more in corrosion resistance for metals in a different industrial context, while green lead is less common and does not possess the specific attributes that make yellow chromate ideal for highway environments.