For most drivers in the United States, obeying a stop sign when approaching an intersection is an unavoidable annoyance. But for Jiasun Li, professor of finance at George Mason University, it’s a problem waiting to be solved.
recent sound work document proposes a simple and inexpensive improvement: remove a stop sign at each four-way intersection. According to his calculations, this would not only increase driver safety, but also environmental sustainability.
Li specializes in game theory, which models strategic interactions where rational agents seek — as humans typically do — to optimize outcomes for themselves. As he drove around Fairfax, Virginia, Li couldn’t help but see the four-way intersections through this academic lens.
He was struck by the suspicion that having four stop signs at an intersection was an imperfect way to prevent traffic accidents. In effect, they reduced the potential cost of not stopping at the intersection, as drivers could assume that motorists coming from other directions, if any, would stop. Drivers turning right, a shallower maneuver with less exposure to oncoming traffic, have the least risk initially and would be most likely to ignore the sign.
Li assumed that the outcome of all conductors obeying the sign was less than the term of a Nash-game-theoretic equilibrium for a stable set of standards that all parties are incentivized to follow.
His working paper presents mathematical models that support his intuition. By comparing the risk of collision with the gains from ignoring the sign (i.e. smooth driving experience or fuel conservation), he finds that a symmetric balance under the current mechanism four-sign is one in which left-turners and straight-line travelers honor the stop sign, but right-turners do not.
In real life, of course, the fear of being slapped by a moving offense increases the likelihood of obeying stop signs. But the need for law enforcement is far from ideal, Li says. If the four-way arrest system applied itself, expensive police resources could be directed to serious crimes and away. preventive penalties for traffic offenders.
Li’s working paper first examines what would happen if traffic laws were changed to allow right-turners to operate the stop sign legally. In an intersection with four stop signs, this would indeed prevent accidents. However, many U.S. intersections only have two signs, which would put right-turners at risk of colliding with traffic coming from the left. Additionally, Li argues that old habits die hard, including behind the wheel.
“If you need people to change their behavior, it’s going to be difficult,” he says.
Instead, Li recommends removing one sign – any sign – among the four. In this case, drivers would know that running a stop sign could send them directly into the path of an oncoming car that has not been instructed to stop. Universal fear would encourage compliance without relying on the threat of police sanctions. “It is important to note that although the safety and incentive analysis relies on game-theoretical reasoning, once implemented, a three-sign mechanism does not require any change in behavior for law-abiding drivers” , Li said.
Moreover, the calculations deep inside Li’s envelope suggest that his relatively mundane change could have a surprisingly large impact. Based on official statistics from various US authorities, he estimates that there are approximately one million four-way intersections with stop signs in the United States, each of which is crossed by more than 760,000 vehicles per year. This represents more than 760 billion (760,000 x one million) stops and starts per year, of which a quarter (190 billion) would be avoided in a three-panel configuration.
According to Li’s calculations, assuming that it takes 124.9 kilojoules of work to bring a medium-duty car to a complete stop, and the same amount to resume the previous speed level, adopting a three-sign system would allow save a total of 118.65 trillion kJ in the United States per year. This equates to one billion gallons of gasoline, or about 2.7 days of national gas consumption.
Looking further out on the technology horizon, Li speculates in the paper that “when self-driving cars finally become real, our new, simpler mechanism could also save AI computational costs.”
Li is under no illusions about the resistance his recommendation might provoke. “You challenge people’s conventional wisdom. If there are criticisms, it is normal. For example, some cops might not like this idea, because I’m taking away one of their sources of income, even though there might be an overall gain for the whole society.
This article is just one manifestation of what Li sees as a scientific mission to apply new perspectives—in this case, an economic perspective derived from game theory—to real-world problems, especially those that have been taken for granted for so long that they are not even recognized as problems.
“Economic thinking should apply to many different fields and improve our daily lives,” Li says.
What seems totally natural in one context, after all, may be foreign in another. Many countries, including China, where Li was born, do not use four-way intersections. “If I had grown up with these stop signs, I probably wouldn’t think about it,” he says. This is an example, Li suggests, of how diverse experiences and ideas imported through immigration can enrich receiving countries. Far from wanting the final say on the matter, Li hopes to inspire a broad conversation about how to change environments and communities for the better.
“I prefer the discussion to continue and people to give me ideas,” he says. “It’s only through debate that people will understand it better.”