Passing on the right is legal in which of the following scenarios?

Passing on the right is legal in specific situations to enhance traffic flow and safety. In the context of the given question, a four-lane highway that accommodates two lanes of traffic in each direction allows for the safe execution of passing on the right. When vehicles in the left lane are either making a left turn or moving more slowly, it becomes permissible to pass on the right as long as the conditions are safe and there is adequate space.

Additionally, on a one-way street, all traffic flows in a single direction, and thus, vehicles may legally pass on the right as there are no vehicles facing oncoming traffic to create a conflict. The uniform direction of travel on a one-way street provides a clear context where passing on the right is not only legal but often necessary for efficient movement of traffic.

These situations illustrate how traffic laws are designed to facilitate safe driving practices while promoting the smooth flow of vehicles on the road.