Dipping Headlights: An Iterated Prisoner’s Dilemma or Assurance Game

When two cars meet in the dark on a rural road, and both drivers use their headlights on full beam, they will both be dazzled. Because of that, we usually dip the lights. However, if modelled as a finite Prisoner’s dilemma super-game, the standard game theoretic solution would be that both drivers defect and use full lights throughout the super-game. Several different strategies are presented and discussed, in particular whether the strategy most often used by drivers, can be invaded by the strategy novice drivers learn in their driver education. On theoretical grounds one could expect the cooperation to unravel because novice drivers are taught to defect both in the beginning and at the end of the super-game. However, empirical results from three different surveys reveal that novice drivers change their behaviour and adapt to normal practice with experience in real traffic. Hence, cooperation has sustained because cooperative and retaliating strategies dominate in the population. In addition, when drivers retaliate by flashing their headlights, it is probably perceived as a negative penalty which causes the inexperienced drivers to adjust the behaviour to normal pactice.