Which lane is generally used for passing another vehicle?

The left lane is generally used for passing another vehicle because it is designated as the lane for faster-moving traffic on many roads, particularly highways. This lane allows drivers to safely overtake slower vehicles in the right lane without having to reduce their speed. The left lane facilitates smoother traffic flow by keeping faster vehicles together and minimizing interruptions in the right lanes, which are typically used for cruising or entering/leaving the roadway.

In contrast, the right lane is primarily for local traffic, vehicles preparing to turn, and those joining or leaving the road. The middle lane may serve various purposes depending on the road design, but it is not specifically designated for passing in most circumstances. The emergency lane is meant for breakdowns and emergencies and should not be used for driving or passing. Therefore, the left lane is the preferred choice for passing due to its function in encouraging efficient traffic movement.