Final answer:
A pair of unbroken double-yellow lines indicates no passing and acts as an imaginary wall separating opposite lanes of traffic, crucial for traffic safety.
Step-by-step explanation:
A pair of unbroken double-yellow lines several feet apart on the roadway indicates that no passing is allowed and acts as an 'imaginary wall or divider' that separates lanes of traffic moving in opposite directions. These lines mean that you cannot cross them to overtake or pass another vehicle. It is essential for drivers to understand this rule for the safety of all road users. This kind of road marking is there to maintain traffic safety and order on roads where visibility or other factors make passing dangerous.