What is the purpose of the passing lane on a highway?

The purpose of the passing lane on a highway is to enable drivers to overtake slower vehicles. This lane is specifically designed to aid in safe and efficient traffic flow, allowing vehicles that are traveling at a faster speed to maneuver around those that are moving more slowly. When used correctly, passing lanes can help reduce congestion and improve travel times by allowing quicker vehicles to advance without causing undue delays for others.

The other choices do not accurately reflect the primary function of a passing lane. Passing lanes are not meant for excessive speed; instead, they allow overtaking while still adhering to speed limits. Additionally, they are not designated solely for emergency vehicles or for making left turns, as those functions are typically served by other traffic designs on the roadway.