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Universal Ethics
Universal Ethics > Research > Emergence of a Rule > Basic Simulation


Imagine that we are redisovering the origins of transportation, when people were first driving their new-fangled cars over the first dirt roads. No rule had been established whether to pass on the left or on the right when meeting an oncoming car. Sooner or later each car will meet another one coming toward it on a road: let's see what happens then...

The first time any driver encounters another driver, each of the drivers slows down their vehicle because they are afraid of a collision. Not knowing which side to pass on, each makes a random choice of left or right. This encounter can lead either to a safe pass, or to an unwanted panic in which drivers must stomp hard on their brakes or drive into the ditch.

Wishing to avoid collisions, each driver remembers the results of each encounter, and makes future choices of left vs right passing based on his experience. (If right hand passing has worked better for him than left hand passing, he will pass on the right. If left hand passing has worked better for him than right hand passing, he will pass on the left.)

What do you think will happen? Will the drivers continue going around bumping each other indefinately? Or will a rule emerge? Keep in mind that the choice between left and right passing is entirely random for the first encounter of each driver.

Have you made your guess of what will happen? If so, click the button below, and the simluation will run 50 days of encounters among 100 cars, with a rate of one encounter per car per day.

Cars driving to daily activities...

When you click the button, simulation results will appear here.

What Happened?

After you press the button, the chart shows the results at the end of each day. The counts in the two columns show how many cars prefer to pass on the left and how many prefer to pass on the right.

As you can see, in the first day there is an approximately equal number of cars with each of the two preferences. On subsequent days, cars continue to gain experience in the same manner. The driver's preference will depend on which of the two passing strategies has been most successful for him.

Watch to see if one side or the other becomes more popular, and how long it takes. Try pressing the button again to re-run the simulation. What happens? Does the same preference emerge each time?

Because the encounters produce random results, it might surprise you to see that all drivers eventually choose one side or the other. However, this is a well known phenomenon in statistics known as a random walk.

Think about right-hand vs left-hand passing rules in various nations. Nations that were isolated from others in the real world have developed different rules: In England and Australia, passing on the left is standard, while in USA, Canada, and France, passing on the right is standard. There is no way to prove that one way is better than the other. But there is a guiding force that leads to a rule rather than continuing with the lack of one: people don't want to risk collisions! So, even when lacking any leadership that would decide the matter, people's actions serve as votes that eventually result in a behavioral standard.

How does the Simulation work?

The simulation is written in Javascript and embedded in the web page. For those of you who are familiar with computer programming concepts, here is an english language equivalent of the computer program:

For each of 50 days
- For each of 100 simulated drivers
- - Randomly select another driver for the encounter
- - If the first driver has no preference of left or right
- - Then he makes a random choice
- - Else he chooses the side that has been most successful for him.
- - If the second driver has no preference of left or right
- - Then he makes a random choice
- - Else he chooses the side that has been most successful for him.
- - If each car chooses the left
- - Then count that as a success for each of them on the left
- - Else they haven't chosen the left
- - - If each car chooses the right
- - - Then count that as a success for each of them on the right.
- - - Else they have made opposite choices (head on!)
- - - - The first car counts a failure for the choice it made.
- - - - The second car counts a failure fo the choice it made.
- Next driver (go back to repeat for the next driver)
- Tally the results for the day and show the results in the table.
Next day (go back to repeat for the next day)

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