passing lane

A passing lane (North American English) or overtaking lane (British, Irish and Australian English) is the lane on a multi-lane highway or motorway closest to the center of the road (the central reservation). In Californian terminology, the passing lane is often known as the number one lane, left lane, or leftmost lane, due to left hand drive (driving on the right), and the rightmost slow lane is sometimes called the "outside lane", because the lane nearest the center of the roadway is considered "inside". Some regions of the world reverse the definitions of "inside" and "outside", as described under #Regional terminology.