On a multi-lane highway, when is it legal to drive on the left side?

Driving on the left side of a multi-lane highway is primarily legal when a driver is overtaking another vehicle. This rule is designed to maintain traffic flow and safety. When you see a slower vehicle in your lane, it becomes necessary to move to the left lane to safely pass that vehicle. This maneuver allows for a more efficient movement of traffic, reducing congestion and maintaining proper lane discipline.

The other scenarios provided, such as driving at the speed limit or making a right turn, do not justify being in the left lane. The left lane should primarily be reserved for passing slower vehicles or for drivers who wish to travel at higher speeds, as remaining in that lane without overtaking can impede the flow of traffic. Similarly, being stopped at a traffic signal does not relate to lane usage, as vehicles should be positioned in the appropriate lane according to their intended direction of travel when the light changes.