Used to define an occurrence of traffic activity in and around Pittsburgh, PA - particularly, if there are at least two drivers at an intersection with a red light, and one is attempting to make a left turn while the other is continuing straight, it is 'customary' for the individual continuing straight to allow the individual making a left turn to go first when the light initially turns green. This is contrary to normal traffic law, especially in the commonwealth of PA, which states that any vehicle making a left-turn must ALWAYS yield to vehicles continuing straight through an intersection.

While technically illegal, the actions are intended most courteously - this is because, unlike many major cities, Pittsburgh differs in the fact that it contains more two lane roads (one lane in each direction), including bridges, than any other style of road (two or more lanes in each direction); even the major highway systems are only two lanes in each direction. As well, Pittsburgh has more two-lane road intersections missing 'left-turn lane only' lanes than most major cities.

The 'Pittsburgh left' helps maintain an efficient flow of traffic throughout the city, particularly during rush-hour; while traffic law requires the left-turning vehicle yield to on-coming traffic for safety reasons, the 'unorthodox' left-turn helps minimize delays incurred by the overall traffic system. When the left-turning vehicle yields to oncoming traffic on a two-lane road, the traffic behin...