Drivers must use the left lane on a highway for:

Using the left lane on a highway primarily serves two purposes: facilitating passing and accommodating fast-moving traffic. The left lane is generally designated for vehicles that are overtaking slower vehicles in the right lane or for those traveling at higher speeds. This arrangement helps maintain the flow of traffic and reduce congestion.

While turning left is a specific maneuver that can be performed in the left lane, it is not the primary reason for its use on highways. The right lane is typically utilized for slower or standard-speed traffic, making the left lane a critical space for those needing to maneuver around slower vehicles or to drive faster when safe.

By adhering to lane usage laws that designate the left lane for passing and fast-moving traffic, drivers contribute to a safer and more efficient driving environment on highways.