Final answer:
Double solid centerlines are road markings that indicate no passing zones, commonly found in areas with limited visibility where overtaking is unsafe.
Step-by-step explanation:
Double solid centerlines are commonly found on roads where overtaking or passing is prohibited due to safety concerns. These lines indicate that neither direction of traffic can cross the lines to pass. They are typically seen in areas where visibility is limited, such as on curves or hills, where it is unsafe for vehicles to be in the opposing lane. The presence of double solid lines means that you should stay in your lane and follow the traffic flow until the road markings indicate that it is safe to change lanes or pass.