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

Driving in the left lane on a highway is acceptable primarily when passing another vehicle. The left lane is typically designated for faster vehicles and for overtaking slower traffic. This rule helps maintain a smooth flow of traffic and reduces potential congestion that can occur when slower vehicles remain in the left lane.

While it may seem appropriate to drive under the speed limit or when tired, these scenarios do not justify occupying the left lane, as it can obstruct faster-moving traffic. Additionally, heavy traffic usually warrants staying in the right lane to allow for smoother movement and higher safety standards on the road. Thus, passing another vehicle is the primary reason for utilizing the left lane, ensuring that the highway operates efficiently and reduces frustration for all drivers.