Final answer:
A solid double line down the center of a roadway signifies a "no passing zone." This means that drivers are not allowed to pass other vehicles on the roadway.
Step-by-step explanation:
A solid double line down the center of a roadway signifies a "no passing zone." This means that drivers are not allowed to pass other vehicles on the roadway. The purpose of the double line is to ensure the safety of all drivers on the road by preventing risky overtaking maneuvers that can lead to accidents.