Prisoner's Dilemma Driving at Night

While I enjoy the fall and pumpkin spice related items, the earlier sunset made my drive home from the store a little darker than usual. Being a rational actor, I turned on my headlights but was somewhat disappointed by how little they lit up the road. Knowing the high-beam function provides almost daylight-like lighting, I also turned this on. However, when coming across other cars I habitually turned the high-beams off. Thinking back to the tests for both learner's permit and full license, as well as the driver's ed course I took, I don't recall ever hearing any laws about high beams. While I remember my parents telling me to only turn them on when the road ahead is empty, I always thought it was just a courtesy. Thinking more about this, I realized the situation is a typical prisoner's dilemma. Leaving high-beams on improves the visibility of the road to the driver with them on, while negatively impacting other drivers. In the payoff matrix below, the numbers represent visibility as drivers pass one another on a road at night. Let's say 100% is daytime or full visibility. Using high-beams gets a driver close to full visibility (90%) if the other driver is using standard headlights while causing the other driver to hardly see anything (30% visibility). The best position for all drivers to be in is the bottom right, but both drivers could potentially increase their visibility by turning on their high-beams if the other driver doesn't. If both act out of self-interest, they will end up in the top left at 40% visibility, a dangerous position when driving at high speeds.

	Use high-beams	Use standard headlights
Use high-beams	40\40	90\30
Use standard headlights	30\90	80\80

Because of this, a law requiring high beams to be turned off when around other cars would perfectly fit what we learned in class, forcing the two drivers in this game to the bottom right. After some research, I was able to find that all states in the US do have high-beam laws that intend to keep drivers in the bottom right quadrant.