What does a yellow line placed in the centre of the road imply?

A yellow line placed in the center of the road signifies that no vehicles may park on either side except for emergency vehicles. This marking is crucial for maintaining the flow of traffic and ensuring safety on the roadways. It helps to indicate that the area is not designated for parking, which is important in areas where stopping or standing could impede traffic or create hazards for other drivers. Emergency vehicles are usually allowed to stop temporarily in specific areas to respond quickly in case of emergencies, but general traffic must remain clear.

The other options relate to various parking allowances that would contradict the purpose of a yellow line, which is intended to prevent parking to facilitate safe and efficient movement of vehicles.