Of Human Action but not Design

Munger has an article trying to explain the evolution of cultural but not legal norms and uses as his example the so-called Pittsburgh Left Turn (said to be responsible for Roethlisberger's motorcycle accident.)

In an article in the Pittsburgh City Paper in 2006, Chris Potter wrote:

As longtime residents know, the Pittsburgh Left takes place when two or more cars — one planning to go straight, and the other to turn left — face off at a red light without a "left-turn only" lane or signal. The Pittsburgh Left occurs when the light turns green, and the driver turning left takes the turn without yielding to the oncoming car.

Pittsburgh is an old city, many of whose streets were designed before automobiles held sway. [That means] that street grids are constricted, with little room for amenities like left-turn-only lanes. The absence of such lanes means drivers have to solve traffic problems on their own. Instead of letting one car at the head of an intersection bottle up traffic behind it, the Pittsburgh Left gives the turning driver a chance to get out of everyone else's way. In exchange for a few seconds of patience, the Pittsburgh Left allows traffic in both directions to move smoothly for the duration of the signal. Of course, the system only works if both drivers know about it. No doubt that's why newcomers find it so vexing.

The Pittsburgh Left is a very efficient convention. On two-lane streets, turning left can block traffic as the turning car waits for an opening. And left-turn arrows are expensive and add time to each traffic light cycle. Far better to let the left turners — if there are any — go first. If there are no left turners, traffic just proceeds normally, not waiting on a left arrow.

Actually, it’s worse than that. The Pittsburgh Left is technically illegal, according to the Pennsylvania Driver’s Handbook (p. 47): “Drivers turning left must yield to oncoming vehicles going straight ahead.” The written rules, the gamer rules, appear to endorse one pattern of action. But the actual rules, the ones you have to travel around to learn, may be quite different. Real rules are not written down, and the people living in that rule system may not understand either the nature or effects of the rules. It is very difficult to change conventions, because they represent the expectations people have developed in dealing with each other over years or decades.

As Hayek said in 1988, in The Fatal Conceit:

To understand our civilisation, one must appreciate that the extended order resulted not from human design or intention but spontaneously: it arose from unintentionally conforming to certain traditional and largely moral practices, many of which men tend to dislike, whose significance they usually fail to understand, whose validity they cannot prove, and which have nonetheless fairly rapidly spread by means of an evolutionary selection — the comparative increase of population and wealth — of those groups that happened to follow them.… This process is perhaps the least appreciated facet of human evolution.