It’s the wee hours of the morning, and the streets are empty, but you’re stuck at an endless red light. A smart traffic-light system could alleviate your frustration. In fact, Israeli technology startup NoTraffic conducted a study in Redlands, California, in which they found that smart traffic lights reduced average delay time at intersections by about 40% and enabled signals to be 14% more green than yellow. In operation at only 2% of city intersections during their two-month test, the system eliminated 900 hours of driver delays. Moreover, fewer drivers ran red lights.

Google has been working on similar technology. In 2021, the company found that its smart traffic light system cut fuel use and traffic delays by 10 to 20%. Similarly, Chinese tech giant Alibaba rolled out its City Brain system to the entire city of Hangzhou in 2017. The company used a mapping app as well as hundreds of thousands of cameras to monitor vehicles in the city of 10 million people. After successfully improving traffic flow, City Brain is now being used in several major cities.

Why do we Need Smart Traffic Lights?

Our 21st-century roads differ greatly from those of 1912 when Lester Wire, a young Salt Lake City police officer, came up with the idea for traffic light signals. Traditional traffic lights typically operate on a timer that is programmed based on periodic traffic counts. While timers are digital nowadays, most traffic lights aren’t much smarter than they were in 1914 when the first electronic light was installed in Ohio. They just aren’t built to handle modern traffic problems: a greater number of cars, larger road networks, higher population densities, and constant traffic disruptions. Smart traffic lights can help alleviate these problems by more efficiently moving traffic through intersections.

What are Smart Traffic Lights?

Smart traffic lights are internet-connected vehicle traffic control systems capable of adapting traffic light activity based on information from sensors, edge devices, and video systems. They create a more intelligent traffic management system that reduces congestion and travel times, improves safety, and reduces carbon emissions.

Smart traffic lights look identical to regular traffic lights except for extra hardware elements such as IoT (Internet of Things) sensors and/or connected CCTV cameras. On the back end, smart traffic light systems are connected to a cloud-based traffic management platform.

How do Smart Traffic Lights Work?

Smart traffic signals are equipped with sensing, video capture, and connectivity technologies to collect real-time data from the environment. The obtained data is either pre-processed on the device or transmitted to a cloud-based transport management system, where it’s processed by a predictive traffic light algorithm that generates instructions for signal adjustments.
A smart traffic light unit still has the familiar red/yellow/green three-light interface, plus:

  • Smart traffic signals are equipped with sensing, video capture, and connectivity technologies to collect real-time data from the environment. The obtained data is either pre-processed on the device or transmitted to a cloud-based transport management system, where it’s processed by a predictive traffic light algorithm that generates instructions for signal adjustments.
  • Ability to collect and exchange data with connected cars, onboard vehicle computers, telematics systems, cloud-based traffic platforms, and mobile travel or driving apps
  • Sensors
  • Radar/LiDAR (light detection and ranging)
  • Speed detection
  • Weather sensors
  • Emissions capture sensors
  • Connected cameras with real-time traffic detection capabilities
  • Red-light running monitoring
  • Pedestrian and traffic-flow detection
  • Vehicle detection for traffic counts
  • Accident detection
  • Onboard computer

The exact configuration differs by manufacturer. Some smart traffic lights have more advanced sensing capabilities; others just rely on camera footage. NoTraffic, for example, uses IoT sensors that rely on radar and computer vision for smart signaling and captures car data in DSRC (dedicated short-range communications) and C-V2X formats. C-V2X, also known as Cellular V2X, is a 3GPP (3rd Generation Partnership Project) standard for V2X applications, such as self-driving cars, that is an alternative to 802.11p (also known as WAVE), the IEEE specified standard for V2V (vehicle to vehicle and other forms of V2X) communications. On-device/on-edge road data pre-processing reduces latency. With suitable hardware, you can run baseline traffic conditions analysis on a smart traffic light device. For example, such roadside units can:

  • Analyze vehicle movements at intersections to detect violations
  • Count vehicles to adjust signal timing
  • Estimate emissions levels to inform urban planners

On-edge processing is a pillar for implementing adaptive traffic signals control (ATSC) — real-time traffic signal adjustments based on the current road situation. ATSC systems can reduce vehicle wait time by 40%, cut travel time by nearly 26%, and lessen vehicle emissions by 21%, according to Carnegie Mellon University. Digital traffic signals can dispatch pre-processed and raw data to a connected cloud-based control center, such as an intelligent transport system (ITS). Here you can perform more advanced modeling and predictive analysis to stave off traffic congestion and harmonize public transport schedules. Likewise, you can use historical data collected by edge devices to build advanced models for:

  • Traffic prediction
  • Parking management
  • Multimodal transportation planning
  • Mobility as a Service (MaaS) solutions

Benefits of Smart Traffic Lights

Reduce traffic: smart traffic lights react to changing traffic patterns in real-time, adjusting the length of green and red lights to move traffic more efficiently.

Protect pedestrians: Smart traffic lights can sense the presence of pedestrians, bicyclists, and wheelchair-bound individuals, alert drivers to their presence, and stop traffic to allow them more time to cross an intersection.

Support emergency response vehicles: Smart traffic lights enable emergency response vehicles to reach their destination more quickly by dynamically changing traffic signals to keep traffic flowing en route to the emergency and by blocking cars from entering intersections before first responders have passed through.

Limit carbon emissions:Smart traffic lights lessen carbon emissions by reducing the amount of time vehicles idle at red lights, a significant source of greenhouse emissions that generates up to 30 million tons of carbon dioxide each year, according to the U.S. Department of Energy.

Increase safety on city streets: Smart traffic lights increase safety by reducing driver frustration that leads to distracted or aggressive driving, adapting signaling to accommodate difficult weather conditions, and better managing the flow of vehicles, pedestrians, and bicycles through intersections.

Smart Traffic Light Case Studies – Germany and the United States

Researchers recently collaborated with city planners in Lemgo, Germany, on an AI program for traffic light management. The team used a set of high-resolution cameras and radar sensors to capture traffic data. They then trained a deep learning algorithm to regulate signaling at a busy intersection, tasking it with estimating the optimal switching behavior for the traffic lights, determining the best phase sequence to reduce waiting times, detecting average journey times in the area, and reducing noise and CO2 emissions. During the simulation run, the algorithm managed to achieve a 10 to 15% improvement in traffic throughout the tested area.

Equally impressive were the results of a recent U.S. study of smart traffic signal preemption for emergency vehicles. In Fairfax County, Virginia, a preemption system enabled emergency vehicles to pass busy areas faster and with fewer conflicts, saving 30 to 45 seconds per intersection. In the city of Plano, Texas, a similar solution reduced the average number of emergency vehicle intersection crashes from 2.3 per year to less than one every five years. They also managed to maintain the same response times with fewer fire and EMS stations in the area.

Have you had any experiences working with smart traffic lights? Let us know your thoughts below.