Maybe you were the fool who waited too long to turn left at the yellow light until there was a gap in the crowded oncoming traffic, meaning I, and the many more drivers who were soon in your lane, were stuck at the red light, our journeys interrupted because of your poor choice.
What you were doing was completely legal, but at the same time completely wrong, and it is time to put an end to this betrayal.
Why don’t we ban left turns on busy roads in U.S. cities?
Anyone who has driven in a major metropolitan area recently has noticed two unfortunate trends: Traffic is getting slower and more dangerous.
“My Fair City” is a case study of the problem and a testbed for a potential solution.
Last year, Washington’s car travel times were the fifth slowest among North American cities, worse than Boston, Chicago and Los Angeles. During rush hour (an obvious misnomer), DC drivers travel at an average of 14 miles per hour, forcing us to spend an extra 83 hours a year in our cars.
Slower traffic often makes it safer, but congestion, frustration, and the proliferation of smartphones have combined to create a toxic mix. Last year, Washington, DC, recorded its highest number of traffic fatalities in 16 years. Nationwide, pedestrian fatalities have been rising since 2009, reaching levels not seen since 1981.
The three and a half extra days Washingtonians spend driving their Toyotas each year aren’t just caused by people getting stuck behind idiots making left turns on Wisconsin Avenue, nor are they caused by frustrated drivers bravely weaving through oncoming traffic.
But left turns are the big culprit.
According to the National Highway Traffic Safety Administration, more than 9 million vehicles were involved in crashes in 2022. About 11% of these vehicles were turning left at the time of the crash, more than twice as many as those turning right. These left turns also caused more than eight times as many fatalities and about four times as many injuries as right turns. When NHTSA investigated crashes that occurred only at intersections, about 62% of these crashes were caused by left turns.
However, the answer is not to ban left turns altogether, but to only ban left turns in certain places and at certain times.
And Bikash V. Gaya has an algorithm for the job. Gaya, a professor of civil and environmental engineering at Pennsylvania State University, has emerged as the Nancy Reagan of left turns, publishing paper after paper showing why you should say no. “The optimal design for downtown, not just for traffic flow but also for safety reasons, is to use two-way streets and prohibit left turns at all intersections,” Gaya told me.
Gaya said that on most roads in most places, most of the time, people should be able to turn left as much as they want, but on the busiest roads in the busiest cities, when almost no one can turn left, almost everyone will be traveling faster.
For example, in a 2021 analysis, Geyer showed that reducing left turns at a city’s busiest intersections by roughly half could reduce total travel times by about 15%. Other studies have found similar effects: One 2019 study found that reducing just 18 left turns in a German city reduced travel times for drivers in that city by about 12%.
Consider my trip up Wisconsin Avenue. It normally takes 30 minutes round trip, so if I can shave 12-15 percent off that, that’s 3.5-4.5 minutes saved each time. If I make this trip 3 times a week, I’ll save 10 hours a year on this route alone.
Left arrow points in the wrong direction
As complex as Gaya’s traffic flow algorithms are, the logic behind them is simple: Left turns without the green arrows favored by my rival Subaru are total chaos; they cause serious, random delays at large intersections. Left turns, on the other hand, are and Green arrows, while more efficient, add up to small but inexorable delays. These turns require extra “cycles,” a traffic-engineering term for a traffic light that goes from red to yellow to green. On a north-south route, for example, there are two cycles at each intersection, one for each direction. But installing a green left-turn arrow adds two more cycles. Even if these cycles are short (say, 30 seconds), they repeat every few minutes, every hour of the day, and add up to huge delays.
Of course, banning certain left turns might mean some drivers have to take longer to get to their destination, maybe by making three right turns in a row, which adds a few minutes to their trip and causes frustration. But, by Gaja’s calculations, most drivers would get those minutes back because of the time they save elsewhere, plus save even more. It’s the transportation equivalent of a Costco membership. The card costs $60 initially, but most people could save much more by buying it for a year at a discount.
Fewer vehicles making left turns at major intersections means fewer serious crashes and pedestrian injuries. For example, one project in British Columbia found that reducing left turns reduced accidents by more than half. Efficiency increases safety, and safety increases efficiency.
There are environmental benefits, too. In cities, cars use a lot of fuel not only while they’re moving, but also while they’re stationary with the engine running. Fewer left turns for some means fewer idling for many, which means less pollution for all. UPS, which puts about 135,000 vehicles on the roads every day, uses routing software designed to avoid left turns whenever possible. Even if three right turns instead of one left turn were to irritate individual drivers, UPS would save a lot on gas. But what’s a hassle for the guys in brown pants is good for the guys in red, white, and blue: fewer carbon emissions in America’s neighborhoods.
Faster, safer, cleaner: if the idea is so simple, why isn’t it widespread yet?
“It inspires people,” Gaya says.
The real challenge is not traffic engineering but human engineering, because this sensible policy runs headlong into the fossil fuel of cognitive biases that spur opposition in many people.
The first is status quo bias, which is the tendency to believe that the status quo is normal, logical, and fair, rather than simply what is happening now. Disrupt the status quo and many will yell, even if it’s counterproductive.
These cries are even louder when change involves a second cognitive bias: loss aversion. We typically feel the pain of losing something more deeply than the pleasure of gaining that same thing. Take away the currently permitted left turn right and local Nextdoor listings will erupt with flames of indignation and threats of lawsuits.
And because of negativity bias (the tendency to notice the occasional bad thing but not the consistent good things), a driver who wants to turn left and isn’t allowed to will be indignant in the moment, but that same driver won’t notice the steady benefits of driving on a fast-moving road.
But I’m willing to provoke such reptilian-brain opposition because the benefits are so great: reduced stress, increased public safety, cleaner air, etc. Moreover, many cities have recently been enforcing similarly controversial road rules. Some, including Washington, have lowered speed limits. Others, also including DC, have done away with the previously sacrosanct right turn on red.
So here are some simple proposals that could further establish our nation’s capital as a national model for transportation innovation. Left turns will be prohibited on state highways that serve the city’s major arteries, including Georgia Avenue, Massachusetts Avenue, and New York Avenue, from 7 a.m. to 9 p.m. daily.On another street, on another time? Turn, baby, turn.
“That’s a good starting point,” Gaya told me. “If I wanted to, I probably would.”
How about you, maroon Subaru? Want to join in?
