Why Banning Left Turns Is A Good Idea (original) (raw)

For a UPS (United Parcel Service) driver making 200 deliveries a day, the number of possible routes is more than 6.7 x 10143:

6, 689, 502, 913, 449, 135, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000.

As a result, UPS uses an algorithm called ORION to sequence the stops.

ORION optimizes efficiency by minimizing left turns.

Banning Left Turns

According to the National Highway Safety Administration, annually, 800,000 crashes involve left turns.

Those left turns, though, always have a cost. Most typically, we wait for the break in traffic to make the turn. But then, misjudging creates fender benders. The second possibility is the “protected” approach that has the left turn signal. The downside here is the wait, no matter what, even if a turn is possible beforehand. It’s a 60 to 90 second delay that adds to the cycle of a traffic signal. A third, lesser-known approach is the “Michigan Left.” Then, the driver moves past the left turn, makes a U-turn farther up the road, and ultimately turns right. The problem here is the expense of adding to a transportation infrastructure and the extra space it needs.

The cheapest solution is just to prohibit left turns. For UPS (and the rest of us), the benefits can be huge:

Our Bottom Line: The Fallacy of Composition

The fallacy of composition tells us that what is good for an individual is bad when everyone does it. The traditional example is yelling fire in a crowded theater. One person can escape alone but not everyone at the same time. Similarly, at a concert, you can stand up to see the stage better. Not so, though, if everyone gets up. And even with saving, we have the same problem. It can be beneficial for one person to accumulate money for a rainy day. However, widespread saving–the Paradox of Thrift–can diminish economic activity, thereby contracting the GDP.

At this point, concluding, we can return to left turns and their connection to the fallacy of composition. One person enjoying the advantages of left turns won’t have a massive impact on aggregate emissions and society’s time use. But certainly, when we all do it, it will. (Does all of this also sound like the tragedy of the commons?)

My sources and more: Thanks to WSJ for inspiring today’s post. Then, WIRED, CNN, and this paper told the UPS story.