For most drivers in the United States, obeying a stop sign upon approaching an intersection is an unavoidable annoyance. But for George Mason University Finance Professor Jiasun Li, it’s a problem waiting to be solved.
October 20, 2022
For most drivers in the United States, obeying a stop sign upon approaching an intersection is an unavoidable annoyance. But for George Mason University Finance Professor Jiasun Li, it’s a problem waiting to be solved.
His recent working paper proposes a simple and economical improvement: removing one stop sign from every four-way intersection. According to his calculations, this would boost not only driver safety, but environmental sustainability as well.
Li specializes in game theory, which models strategic interactions where rational agents seek—as humans generally do–to optimize outcomes for themselves. As he drove around Fairfax, Virginia, Li could not help but view four-way intersections through this academic lens.
He was struck by the suspicion that having four stop signs at an intersection was a flawed way of preventing traffic accidents. In effect, they lowered the potential cost of not stopping at the intersection, because drivers could assume that motorists from other directions, should there be any, would come to a stop. Drivers turning right, a shallower maneuver with less exposure to oncoming traffic, have the least risk to begin with and would have the greatest incentive to ignore the sign.
Li surmised that the outcome of all drivers obeying the sign fell short of a Nash equilibrium–game theory’s term for a stable set of norms that all parties are incentivized to follow.
His working paper presents mathematical models that support his intuition. Comparing the risks of collision against the gains from ignoring the sign (i.e. a smooth driving experience or conserving gasoline), he finds that a symmetric equilibrium under the current four-sign mechanism to be one in which left-turners and straight-line travelers honor the stop sign but right-turners do not.
In real life, of course, fear of getting slapped with a moving violation increases the likelihood of compliance with stop signs.
