When is it illegal to drive in the left lane on a highway?

The left lane on a highway is often designated for passing slower vehicles and is known as the passing lane. It is illegal to drive in this lane if you are not actively passing another vehicle, as this can impede the flow of traffic and create unsafe conditions.

When the left lane is reserved for passing, it is intended to allow faster-moving traffic to overtake slower vehicles in the right lane efficiently. If a driver remains in the left lane without the intention of passing, it can lead to frustration among other drivers and may even result in dangerous situations, such as abrupt lane changes and tailgating.

Driving in the left lane when it is meant for passing only is a violation of traffic laws in many jurisdictions, making option B the correct choice. The other options present circumstances where it is generally permissible to be in the left lane, either due to the absence of other vehicles or at specific times of day, but they do not align with the legal stipulation regarding usage of the left lane for passing.