Final answer:
Yellow center lines indicate two-way traffic, meaning that traffic flows in opposite directions on either side of these lines, and they play an essential role in road safety.
Step-by-step explanation:
The question relates to road traffic regulations and the specific meanings of road markings. Yellow center lines on a road indicate that there is two-way traffic; meaning that traffic flows in opposite directions on either side of the line. These lines are important for road safety and help in managing the flow of traffic with varying traffic densities. The option that correctly corresponds to the act of having a yellow center line is number 3) two-way traffic. It is important to pay attention to such markings as they provide critical information about road use. For pedestrian safety, it is also vital to have designated crosswalks and traffic signals that permit individuals to cross at appropriate times without having to dodge traffic.