Traffic Lights Are Being Reprogrammed to Stop You From Speeding

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For the better part of a century, the American traffic signal has operated under a single directive: maximize throughput.

The “level of service” is a grading system ranging from ‘A’ (free flow) to ‘F’ (gridlock), which has served as the primary report card for traffic engineers. In this paradigm, a red light was viewed as a failure of the system, a bottleneck to be minimized through widened lanes, slip turns, and permissive signal phasing. The goal was to clear the line of waiting cars and reduce vehicle delay.

Because of a persistent crisis in pedestrian fatalities and bolstered by a massive influx of federal funding through the Safe Streets and Roads for All program, the philosophy of traffic signal operations is changing. The traffic light is becoming an agent of change.

This shift is characterized by a suite of new strategies: “Rest on Red” protocols that hold lights red to calm speeders, the widespread removal of “Right on Red” permissions to protect crosswalks, the implementation of “Leading Pedestrian Intervals” to give walkers a head start, and the deployment of Artificial Intelligence that can “see” a vulnerable road user and extend the green light accordingly.

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The Philosophy Shift

To understand the radical changes occurring in 2024 and 2025, you first need to understand the doctrinal shift in civil engineering that underpins them. For decades, American road design was dominated by the concept of “forgiving design,” which aimed to build roads wide and straight enough that a driver who made a mistake would have ample room to recover without crashing.

While well-intentioned for highways, when applied to urban arterials, this philosophy created “stroads,” which are hybrid streets that encouraged highway speeds in environments filled with pedestrians and businesses.

The 11th Edition of the Manual on Uniform Traffic Control Devices, released in late 2023 and fully integrated into state practices throughout 2024 and 2025, marked a critical departure from this logic. The new standards de-emphasize the “85th-percentile rule,” a long-standing practice where speed limits and signal timing were set based on the speed at which 85% of drivers naturally traveled.

In practice, this created a dangerous feedback loop: if drivers sped up, engineers were often compelled to raise speed limits and retime lights to match that speed to maintain “uniformity.”

The Safe System Approach

The new operating system for American intersections is the Safe System Approach. Unlike traditional models that strive to eliminate all crashes (often by blaming driver error), the Safe System Approach accepts two fundamental truths: humans make mistakes, and the human body is vulnerable to kinetic energy.

This philosophy has birthed a new generation of signal strategies that prioritize human life over vehicle delay. Projects are now evaluated not just on how much congestion they relieve, but on how effectively they reduce the risk of fatal injury. The implications for traffic signals are specific and profound:

Kinetic Energy Management: Signals are now designed to force drivers to slow down before they reach the conflict point. If a crash occurs, it should happen at a speed survivable by the human body (typically under 20-25 mph).

Separation in Time: Instead of asking cars and pedestrians to share the intersection simultaneously, signals increasingly separate them completely using exclusive phases.

Proactive Risk Mitigation: Signals should anticipate risky behavior (like speeding) and intervene before a crash occurs, rather than just reacting to historical crash data.

This shift is not merely theoretical. It is visible in the hardware and software upgrades being rolled out in major metropolitan areas. The traffic controller is shifting from a passive timer to a proactive guardian.

Rest on Red

One of the most aggressive and counterintuitive strategies gaining traction in 2025 is the concept of “Rest on Red.” Traditionally, traffic signals on major arterial roads are programmed to “Rest on Green.” This means that in the absence of cross-traffic (such as late at night), the light remains green for the main road indefinitely.

While efficient, this signals to drivers that they have a clear runway, psychologically encouraging speeding on wide, empty roads during off-peak hours, a time when fatal crashes are disproportionately high due to impaired or reckless driving.

How It Works

“Rest on Red” flips this default setting. At designated times (usually late night/early morning), the signal rests in a red phase for all directions. As a vehicle approaches the intersection, loop detectors or radar sensors measure its speed and presence.

The Compliant Driver: If the vehicle is traveling at or below the speed limit, the sensors detect it typically 400 to 800 feet upstream. The system calculates the arrival time and triggers the light to turn green just before the driver arrives at the stop bar. The driver experiences a “green wave” and does not have to stop, maintaining momentum.

The Speeding Driver: If the vehicle is detected traveling above the threshold, the signal holds the red light. The driver is forced to brake and come to a near or complete stop before the light changes. This breaks the “feedback loop” that rewards speeding with uninterrupted travel. The intersection effectively acts as a dynamic speed bump.

Albuquerque’s Experiment

Albuquerque, New Mexico, has served as a primary testing ground for this technology. Lead and Coal Avenues are one-way arterials that connect the university area to downtown. Historically, these streets resembled highways, with drivers frequently exceeding the 30 mph limit by significant margins, leading to a high frequency of severe crashes.

In the pilot program, which expanded through 2024, the city installed radar detection systems linked to the traffic controllers.

Results: Early data and reports from municipal officials indicated a significant reduction in top-end speeding. “We’ve pretty much completely eliminated all of those speeders that are going far above the speed limit,” reported Dan Mayfield from the Albuquerque Department of Municipal Development.

Community Reaction: The implementation was not without controversy. Some residents expressed confusion, noting that without adequate education, drivers might not understand why the light was red, potentially leading to frustration or red-light running if they felt the signal was malfunctioning. Critics also pointed out a “punishment proximity” issue: on multi-lane roads, a law-abiding driver could be forced to stop because a speeder in the adjacent lane triggered the red light hold.

Portland’s High Crash Network

Portland’s Bureau of Transportation has integrated “Rest on Red” into its Vision Zero Action Plan Update 2023-25, specifically targeting the “High Crash Network,” the 8% of streets that account for a majority of traffic deaths.

PBOT focuses on nighttime operations. By defaulting signals to red, the city aims to remove the “runway effect” of empty arterials like Powell Boulevard. This strategy is paired with the expansion of automated speed cameras, creating a dual layer of enforcement (physical signal timing and financial penalty).

Public sentiment has been mixed but leans toward acceptance of safety trade-offs. Community discussions highlight that while the “stop and go” nature can be frustrating for late-shift workers, many residents recognize it as a necessary check on the rampant reckless driving observed since 2020.

Milwaukee’s Rollout

In 2024, Milwaukee began upgrading its 780 signalized intersections with remote control capabilities, allowing for the centralized implementation of “Rest on Red” timing plans. This rollout sparked a classic debate between “traffic flow” and “traffic safety.”

Some residents expressed frustration, arguing that encountering red lights on an empty arterial makes them want to speed up to “catch” the next green, a phenomenon known as “signal racing.” However, city officials countered that uninterrupted flow is “a recipe for speeding” and that “Rest on Red” is a smart, adaptive tool for the modern urban environment. The city’s stance reflects the broader shift in the profession: “Uninterrupted flow is no longer the M.O. of urban traffic managers.”

Costs and Implementation

Implementing “Rest on Red” is often more a matter of software logic and sensor fidelity than heavy civil construction, making it a cost-effective retrofit for cities with modern controllers.

Hardware Requirements: The system requires advanced detection loops or radar units capable of measuring speed at a significant distance.

Cost Efficiency: Compared to physical traffic calming (speed humps, chicanes), “Rest on Red” is relatively inexpensive, costing primarily the price of sensor upgrades (approx. $5,000 – $15,000 per intersection) rather than major concrete work.

Operational Limitations: The strategy is most effective on isolated intersections or corridors with long spacing. It is difficult to implement in a tightly coordinated downtown grid where “Rest on Red” might disrupt progression for the entire network, causing gridlock once volumes rise.

Green Waves Reimagined

For decades, traffic engineers timed lights to create a “Green Wave”: if you drove at the design speed (often 35-45 mph), you would hit every green light. This was designed for efficiency. Today, cities are retiming these waves for safety, explicitly using the signal progression to cap vehicle speeds.

The 20 MPH Progression

In cities like Cambridge, MA, and parts of New York City, signal progression is being re-tuned for 20-25 mph. The physics of the “wave” remain the same, but the target velocity has changed.

Mechanism: If a driver accelerates to 35 mph, they will arrive at the next intersection while the light is still red, forcing a stop. If they stay at 20 mph, they glide through. This effectively uses the traffic signal network as a distributed speed governor.

Psychological Impact: This retiming breaks the habit of “racing to the next light.” Drivers quickly learn that speeding yields no time advantage, only increased brake wear.

Bicycle Green Waves

A more specialized application is the “Bicycle Green Wave,” where signals are timed for bicycle speeds (typically 12-15 mph). Cities like San Francisco and Portland have implemented these on key cycling corridors.

Implementation: Signs are posted indicating “Signals Set for 14 MPH.” This not only helps cyclists maintain momentum (crucial for physical exertion) but also acts as a traffic calming measure for cars sharing the road. A car traveling at 30 mph on these streets will hit every red light, discouraging the use of these corridors as cut-throughs.

While the US is adopting this, international examples like Singapore’s GLIDE system show the potential of fully adaptive waves that prioritize “heavy flow” rather than just speed, though they emphasize that “sticking with the crowd” (and thus the speed limit) is the best way to catch the wave.

The End of Right on Red

Perhaps the most visible and contentious change in American traffic management is the rapid rollback of “Right on Red” permissions. Permitted universally in the U.S. since the Energy Policy and Conservation Act of 1975 (as a fuel-saving measure), ROR is now viewed by safety advocates as a primary source of conflict between vehicles and pedestrians.

Why It’s Dangerous

When a driver prepares to turn right on red, their attention is almost exclusively focused to their left, scanning for oncoming vehicle traffic. To get a better view past parked cars or street furniture, they often inch forward into the crosswalk (a behavior known as “encroachment”).

This creates a critical safety failure:

• The driver blocks the path of pedestrians approaching from the right
• The driver, spotting a gap in traffic, accelerates suddenly
• The driver fails to check back to the right, striking pedestrians or cyclists who have entered the crosswalk with the signal

Washington D.C.’s Data

Washington D.C., has been at the forefront of this movement. Following a City Council decision, bans on turns on red were rolled out to most intersections starting in 2025.

A pivotal study of 100 intersections in D.C. found that No Turn on Red restrictions led to a 92% reduction in drivers failing to yield to pedestrians.

The study concluded that while there were “overall minor impacts to traffic operations” (slight increases in delay), the safety benefits in conflict reduction were overwhelming. This data provided the evidentiary basis for other cities to follow suit.

San Francisco’s Expansion

Following a successful pilot in the Tenderloin district, the San Francisco Municipal Transportation Agency expanded NTOR to 200 intersections in the Financial District, South of Market, and Chinatown throughout 2024 and 2025.

Compliance Statistics: In the initial pilot, 92% of drivers complied with the ban. Close calls (vehicle-pedestrian conflicts) dropped from five per observation period to just one. Crucially, vehicles blocking or encroaching into the crosswalk dropped by over 70%.

Scope: The expansion targets areas with high pedestrian density, prioritizing the “Walkability” of the downtown core over the turning speed of vehicles.

Seattle’s Default Policy

In 2023, Seattle adopted a policy making NTOR the default for new signals and major revisions. By 2025, the city had expanded this to over 41 downtown intersections and key corridors like Aurora Avenue.

Policy Shift: The Seattle Department of Transportation explicitly links this to Vision Zero, noting that pedestrian collisions often involve turning vehicles. The ban effectively creates a “pedestrian-only” phase where the crosswalk is sacrosanct during the walk signal.

Other Cities

• Cambridge, Massachusetts: The city council moved to ban right on red at all traffic lights
• Ann Arbor, Michigan: Adopted a ban in the downtown core
• Indianapolis, Indiana: Downtown bans implemented following a spike in pedestrian fatalities

The Opposition

The rollback of ROR has not been without significant pushback. The friction comes primarily from three distinct sources:

The Delivery Economy: In an era of instant delivery (Amazon, DoorDash, UberEats), time is currency. Drivers argue that NTOR bans increase delivery times and idle time. Online forums for gig workers are rife with complaints about “traps” and tickets in NTOR zones.

The National Motorists Association: This advocacy group opposes blanket bans, arguing that traffic laws should be based on “proven safety interventions while not unduly restricting automobile travel.” They contend that right-turn crashes are a small percentage of total fatal crashes and that bans increase congestion and fuel consumption.

Local Business Concerns: Groups like the Chamber of Commerce often express concern that increased congestion could deter visitors from downtown areas. However, in San Francisco, the Chamber’s opposition has been relatively muted compared to historic precedents, perhaps due to the overwhelming data regarding pedestrian safety in commercial districts.

Despite these concerns, the safety data remains compelling. The trade-off is explicit and intentional: a slight increase in vehicle delay is accepted in exchange for a massive reduction in pedestrian risk.

Leading Pedestrian Intervals

While NTOR bans restrict drivers, Leading Pedestrian Intervals empower pedestrians. An LPI is a simple signal timing adjustment that gives the “Walk” signal 3 to 7 seconds before the parallel vehicle traffic gets a green light.

How It Works

Those few seconds change the geometry of the interaction between the car and the walker.

Visibility: By the time the driver gets the green light, the pedestrian is already in the center of the crosswalk and directly in the driver’s field of vision, rather than obscured on the curb.

Asserting Right of Way: It establishes the pedestrian’s presence, making it psychologically harder for a driver to aggressively cut them off. The pedestrian “owns” the intersection before the car starts moving.

The Safety Data

Recent studies published through 2025 confirm the efficacy of LPIs, solidifying their status as a “best practice.”

Measured Safety Impacts of Leading Pedestrian Intervals

Widespread Adoption

The 11th Edition of the MUTCD has made it significantly easier for engineers to justify LPIs. Previously, engineers often had to prove a specific crash history or volume of pedestrians to warrant an LPI. The new guidelines encourage LPIs as a proactive safety measure rather than a reactive one, removing bureaucratic hurdles.

Los Angeles: LADOT has aggressively installed LPIs, particularly near schools, as part of its Safe Routes to School program. By 2025, more than 75 schools had received these upgrades.

Seattle: Adopted a policy to evaluate adding an LPI every time a new traffic signal is built or maintained, effectively making it the default standard for the city.

AI and Smart Signals

The next frontier of traffic signal technology moves beyond fixed timers to dynamic, intelligent sensing. Passive Pedestrian Detection uses sensors—typically video, thermal, or LiDAR—to identify pedestrians and cyclists waiting to cross or actively crossing, without them needing to push a button.

The Problem with Fixed Timers

Standard traffic signals assume a walking speed of 3.5 feet per second (a standard recently lowered from 4.0 ft/s to accommodate slower walkers). However, this is an average. An elderly person, a parent with a stroller, or a person with a disability may move much slower. Conversely, if a pedestrian crosses quickly, the “Don’t Walk” phase might stop traffic unnecessarily long, breeding driver resentment.

The AI Solution

Cities like Bellevue, Washington, and experimental districts in Florida are deploying “Smart Signals” powered by AI to solve this “dilemma zone.”

Green Extension: If a sensor detects a person still in the crosswalk as the countdown nears zero, the signal controller automatically extends the red light for cross-traffic. The car waits; the person finishes crossing safely. This “empathetic” timing protects the most vulnerable.

No-Push Activation: The system detects a person waiting at the curb and triggers the “Walk” signal automatically. This is crucial for hygiene (post-pandemic) and accessibility (for those who cannot easily reach or press a button).

Conflict Prediction: Emerging AI models, such as those developed by researchers at the University of Hawaii and Texas A&M, can predict potential collisions by analyzing the trajectories of vehicles and pedestrians in real-time. These systems can hold lights red if they calculate a high probability of a driver running the light.

Bellevue’s LiDAR Pilot

Bellevue conducted a “Passive Pedestrian Detection Phase Extension Pilot” using LiDAR technology provided by companies like Outsight. The system creates a 3D point cloud of the intersection, allowing for precise tracking of vulnerable road users day or night, regardless of lighting conditions.

Outcome: The pilot demonstrated the ability to dynamically adjust signal timing to protect slower crossers, resulting in a 56.4% decrease in pedestrian-vehicle conflicts. This technology directly addresses the “Safe Speeds” and “Safe People” pillars of Vision Zero by adapting the infrastructure to the user, rather than forcing the user to adapt to the timer.

Thermal Sensing

Thermal cameras are also being deployed to detect the heat signatures of pedestrians and cyclists. Unlike video cameras, thermal sensors work perfectly in total darkness, fog, or glaring sun, providing reliable detection for “Rest on Red” or LPI triggers without raising privacy concerns associated with facial recognition.

Physical Infrastructure

While signal timing is powerful, it is most effective when paired with physical changes. “Hardened Centerlines” and “Daylighting” are two infrastructure strategies that work in concert with signal operations to force safer driver behavior.

Hardened Centerlines

Left turns are notoriously dangerous because drivers often accelerate to “beat the gap” in oncoming traffic, taking a shallow, high-speed arc that cuts across the crosswalk. This “rushed turn” is a leading cause of pedestrian injury.

The Fix: Cities are installing rubber curbs, bollards, or concrete islands on the yellow centerline of the intersection. This “hardened centerline” modifies the turning radius, forcing the driver to make a squarer, slower, nearly 90-degree turn to avoid hitting the barrier.

Effectiveness:

• Washington D.C.: Vehicle-pedestrian conflicts fell by 71%
• New York City: Turn calming reduced pedestrian injury risk by 16% and fatal crash risk by 80%
• Portland: Median turning speeds dropped by 13%

The physical barrier reinforces the signal logic: even if the light is green (permissive), the physical geometry prevents high-speed maneuvers.

Daylighting

“Daylighting” involves removing parking spaces immediately adjacent to the intersection (typically the first 20-25 feet). This opens up sightlines, ensuring that drivers can see pedestrians stepping off the curb and pedestrians can see approaching cars.

Hoboken, NJ: Often cited as the “gold standard” of Vision Zero, Hoboken has achieved seven consecutive years without a traffic death (as of 2024/2025). A key component of this success is aggressive daylighting (using physical bollards or bike racks) to prevent cars from parking in these critical visibility zones.

New York City: Under the “Universal Daylighting” legislation pushed by advocates, NYC has begun systematically daylighting intersections. However, implementation faces challenges due to the intense demand for parking, leading to the use of “hardened” daylighting (rocks, planters) to physically prevent illegal parking.

Equity and Opposition

The shift toward automated, restrictive signal timing is not just a technical challenge; it is a sociological one. It touches on issues of equity, government control, and the changing nature of public space.

Equity Concerns

Data analysis in 2024/2025 is increasingly focusing on equity. Historically, pedestrian fatalities are disproportionately high in lower-income communities and communities of color, where arterials are wider and infrastructure is older.

Automated Enforcement vs. Police: Technologies like “Rest on Red” and speed safety cameras are viewed by some advocates as a fairer alternative to police stops, which can suffer from racial bias. Automated systems punish the behavior (speeding) regardless of the driver’s profile.

Community Pushback: However, concerns remain that fines from these systems disproportionately impact low-income residents. Cities like Portland are experimenting with non-monetary penalties (warning letters) for first offenses or using revenue strictly for safety improvements in the affected neighborhoods.

The “War on Cars” Narrative

Opposition often frames these measures as government overreach or a “war on cars.” “Rest on Red” is sometimes characterized as a “trap” designed to frustrate drivers. This sentiment is fueled by the American cultural attachment to the automobile and the expectation of unimpeded travel.

However, the “Safe System” counter-argument is gaining traction: the right to life supersedes the right to speed. As summarized by Portland’s Vision Zero update, “No person should die or be incapacitated from using the transportation system.” This moral imperative is slowly shifting the political calculus for local leaders.

Federal Funding

These changes are not happening in a vacuum. They are being propelled by historic levels of federal investment.

Safe Streets and Roads for All

The Bipartisan Infrastructure Law established the SS4A grant program, which provides $5 billion over five years. In 2024 and 2025, billions of dollars flowed directly to municipalities to implement these specific safety strategies.

Grant Requirements: To win these grants, cities must have a “Safety Action Plan.” This requirement has forced hundreds of cities to formally adopt Vision Zero principles and commit to strategies like LPIs, road diets, and signal retiming.

Implementation: Funds are being used for “quick build” projects that include paint, plastic bollards, and signal reprogramming, which can be deployed rapidly compared to major capital construction. For example, Fort Worth received millions for traffic signal upgrades and pedestrian improvements in 2025.

Comparative Costs

Technology Costs per Intersection

While LPIs are cheap, full-scale adaptive signal control with AI detection is expensive. For smaller municipalities without federal grants, the high cost of LiDAR and thermal sensors remains a barrier, slowing the rollout of the most advanced “intelligent” features.

What’s Next

The traffic signal is evolving from a dumb timer into an intelligent, empathetic node in the smart city network.

V2X Integration: Future signals will communicate directly with Connected Vehicles. A signal could theoretically broadcast a “pedestrian in crosswalk” warning directly to the dashboard of an approaching car, or even trigger the vehicle’s automatic emergency braking system if it detects the car is about to run a red light.

Data-Driven Evolution: As cities collect more data from these smart signals, the “High Injury Network” maps will become dynamic. Signals will “learn” which times of day are most dangerous and automatically adjust their aggression (e.g., longer all-red phases, stricter rest-on-red parameters) to compensate.

The era of the “Level of Service” is ending. In its place rises a new metric: “Level of Safety.” By slowing speeders with red lights, giving pedestrians a head start, and using AI to watch over the crosswalk, American cities are redesigning the DNA of the intersection to ensure that everyone—whether in a car, on a bike, or on foot—makes it home alive.

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