Washington State Department of Licensing Knowledge Test

What is the purpose of the solid yellow centerline on highways?

1. To indicate a lane forpassing

2. To separate traffic directions

3. To guide drivers in fog

4. To show speed limits

The correct answer is: To separate traffic directions

The solid yellow centerline on highways serves the primary purpose of separating traffic moving in opposite directions. This visual cue informs drivers that they should not cross the line to overtake or pass another vehicle, thus helping to maintain safe distances between vehicles traveling towards each other. By clearly demarcating the lanes for opposing traffic, it reduces the risk of head-on collisions and enhances overall road safety. The other choices do not accurately represent the role of a solid yellow line. A lane for passing is usually indicated by a dashed line, while guidance in fog is provided through other means like reflective markers or fog lights. Speed limits are communicated through road signs rather than through lane markings. Understanding these distinctions can help drivers make better choices on the road and abide by traffic regulations effectively.