How wide is the solid yellow centerline on a divided highway?

The width of the solid yellow centerline on a divided highway is standardized to ensure visibility and provide clear guidance for drivers. It measures 18 inches wide. This specific width is effective for indicating where the lanes are divided and preventing vehicles from crossing into oncoming traffic.

The significant visibility of an 18-inch line helps enhance safety by clearly marking the boundaries between opposing flows of traffic, especially in low visibility conditions or at night. The other options reflect measurements that do not align with established standards for roadway markings, which are designed for practical effectiveness in traffic management and safety.