Without red lights, intersections would become the most dangerous places in any city. The roughly 300,000 signalized intersections across the United States manage billions of crossing movements every day, and removing them would force drivers, cyclists, and pedestrians into a constant, high-stakes negotiation over who goes first. The consequences would ripple far beyond traffic safety, affecting fuel consumption, carbon emissions, and the basic flow of urban life.
What Happens When Signals Go Dark
We already have a natural experiment for this question: power outages. When traffic lights lose power, drivers are supposed to treat every intersection as a four-way stop. In practice, compliance is uneven. Some drivers slow down cautiously, while others barrel through, assuming they have the right of way. Emergency management agencies urge people to stop at every dark intersection regardless, precisely because so many drivers don’t.
A brief outage at a handful of intersections is manageable. Scale that up to an entire city, permanently, and the system breaks down. Four-way stops work at low-volume intersections, but they create enormous backups when traffic is heavy. A single busy intersection that processes 2,000 cars per hour with a signal might handle a fraction of that volume as a four-way stop, because every vehicle must come to a complete halt, wait its turn, and accelerate again.
The Safety Tradeoff Is More Complicated Than You’d Think
Intuitively, removing signals sounds like a recipe for carnage. And at high-speed, high-volume intersections, it would be. In the U.S., about 260,000 crashes per year are attributed to red-light running alone, resulting in roughly 750 fatalities. Without any signal telling drivers to stop, the potential for broadside collisions (the most deadly type at intersections) would increase dramatically at those locations.
But the picture isn’t entirely one-sided. A study in Philadelphia found that replacing traffic signals with multiway stop signs on certain one-way streets actually reduced crashes by about 24% across all severity levels and conditions. The key difference is context. At lower-volume intersections where signals may have been over-installed, forcing every driver to stop and make eye contact with other road users can be safer than a green light that encourages people to speed through. The problem is that most signals exist at intersections that genuinely need them, where traffic volumes and speeds are too high for a stop sign to manage safely.
Gridlock Would Replace Traffic Flow
Traffic signals don’t just prevent crashes. They create flow. A well-timed corridor of green lights, sometimes called a “green wave,” allows vehicles to move through multiple intersections without stopping. Without that coordination, every intersection becomes a bottleneck. Drivers idle longer, accelerate and brake more frequently, and travel times skyrocket.
The fuel and emissions cost of that inefficiency is staggering. Road traffic already generates about 5.88 billion tonnes of greenhouse gases annually, roughly 12% of all global emissions. Congestion makes it worse. In London alone, congestion-related idling and stop-and-go driving adds about 2.2 million tonnes of CO₂ per year, accounting for 15% of the city’s total road traffic emissions. Paris sees 2.8 million tonnes from congestion, and Berlin adds 420,000 tonnes.
Smart signal timing pushes those numbers in the opposite direction. Research published in Nature Communications found that optimizing traffic signals with adaptive technology across 100 major cities could cut CO₂ emissions by about 6.65%, saving an estimated 31.73 million tonnes annually. That same optimization halved the time drivers spent idling (from 13 minutes to under 7 minutes along test routes) and reduced per-trip CO₂ output by 16%. Removing signals entirely would reverse all of those gains and then some, turning every commute into a stop-and-go crawl.
Alternatives That Actually Work
If red lights disappeared tomorrow, communities would need to replace them with something. The most effective proven alternative is the roundabout. Converting signalized intersections to roundabouts reduces fatalities by 90% and injuries by 75%, according to the Florida Department of Transportation. Roundabouts work because they eliminate the head-on and broadside collisions that cause the worst injuries. Everyone moves in the same direction, enters by yielding, and exits without stopping. They also keep traffic flowing continuously, which reduces idling and emissions compared to signals.
Roundabouts have limits, though. They require more physical space than a traffic light on a pole, making them difficult to retrofit into dense urban grids. They can also overwhelm pedestrians and cyclists when traffic volumes are very high, and they confuse drivers in places where they’re uncommon.
The other alternative on the horizon is virtual traffic management through connected vehicles. In simulations where cars communicate directly with each other, coordinating who enters an intersection and when, researchers at Louisiana State University found that delays dropped by 50% to 97% compared to traditional signals, with no collision risk. That technology depends on every vehicle on the road being equipped and connected, which remains decades away from reality.
The Hidden Cost of Keeping Lights Running
Traffic signals aren’t cheap to maintain, which is one reason some communities consider removing underused ones. Retiming a single intersection costs roughly $2,500 to $3,500, and that needs to happen every few years as traffic patterns shift. Signal controllers require upgrades costing about $10,000 each, ideally every decade. Advanced adaptive systems that respond to real-time traffic run $50,000 or more per intersection to install. Multiply those figures across hundreds of thousands of intersections nationwide and the bill is enormous.
But the return on that investment is hard to argue with. Properly timed signals across 100 cities could save an estimated $15.83 billion per year in fuel costs alone, with total societal and environmental benefits reaching $31.82 billion annually. The cost of not having signals, measured in wasted fuel, lost productivity, medical bills, and lives, dwarfs the cost of keeping them running.
What a World Without Red Lights Would Look Like
In a city without traffic signals, daily life would look fundamentally different. Commute times would multiply as every major intersection became a negotiation. Pedestrians, who currently rely on walk signals to cross safely, would face a constant gamble. Emergency vehicles would lose the ability to trigger green lights in their path, slowing response times. School zones, hospital entrances, and downtown cores would become especially chaotic.
Rural and suburban areas with lower traffic volumes would adapt more easily, since many already function with stop signs and yield signs. But any corridor handling more than a few hundred vehicles per hour would grind to a near halt. The economic losses from delayed freight, missed appointments, and increased fuel consumption would compound quickly. Cities evolved around the assumption that intersections are managed. Remove that management, and the entire system of urban movement unravels.