Smart traffic systems acquire data from the road users and communicate with a central control system to change lights and signal lengths as needed.
Smart traffic systems acquire data from the road users and communicate with a central control system to change lights and signal lengths as needed.
( Source: gemeinfrei / Unsplash)

SMART TRAFFIC LIGHTS Smart city infrastructure improves the journey of road users

Author / Editor: Cate Lawrence / Nicole Kareta

Smart traffic lights create the opportunity to upgrade the road through the use of real-time data resulting in responsive lights to the specific needs of road users. Numerous initiatives are underway to improve the journey of road users, reduce congestion and pollution, and increase safety.

Roads help goods and people around streets, neighborhoods, and cities. Streets are shared by many users, including cars, buses, trucks, bikes, and pedestrians who all want to travel efficiently and safely. We've seen efforts of late to extend pathways for bike users, but designing and altering roads can be an expensive, lengthy enterprise. Fortunately, smart city technology can create a layer of order to streets, changing traffic flow, reducing accidents and pollution, and responding to different needs of road users. An example is smart traffic lights, which can help cities regulate traffic on busy roads and respond to users' specific challenges such as emergency vehicles.

What are smart traffic lights?

Traditional traffic lights are programmed to change signals at predetermined times, such as typical peak hours. If you've ever struggled to cross two sets of lights as a pedestrian before the light turns red, or hit every red light as a driver, despite being the only car on the road, you'll know their impracticality. By comparison, smart traffic systems acquire data from the road users and communicate with a central control system to change lights and signal lengths as needed.

Smart traffic control systems primarily consist of

  • a central control system
  • smart traffic lights
  • cameras and queue detectors

The cameras and queue detectors can monitor and inform the control system of real-time traffic conditions. In turn, the lights can respond according to the information, improving traffic flow, reducing congestion, prioritizing pedestrians, and emergency vehicles. There are numerous capabilities at play in the traffic V2E ecosystem. In the US, traffic systems are more likely to talk to each other, as urban traffic light systems are more uniform and planned over larger areas. In Europe, traffic infrastructure is more local and decentralized, with the technology still being tested and rolled out across vehicles and different systems. There are several key initiatives and benefits to specific road users:


In 2019, Audi introduced vehicle-to-infrastructure (V2I) service "Traffic Light Information" to Ingolstadt, Germany (the technology has been available in much of the US since 2016) with a larger roll out from this year. Audi drivers can see via the dashboard what speed is required to reach the next traffic light on green. If that is not possible within the permitted speed limit, there will be a countdown to the next green phase.

Audi predicts that in the future, their customers may be enjoy added benefits such as cars, which make increased use of braking energy to charge their batteries at red lights. They also predict that predictive adaptive cruise control could enable cars to even brake automatically at red lights.

Smart trucks

In the Port of Hamburg, a trial is underway to optimize a frequent visitor to the ports - trucks. Red lights mean trucks have to completely stop and start again, which is only time-consuming but wastes fuel. By identifying trucks, traffic lights can not only stay green but remain green to enable truck convoys to cross together, reducing overall congestion for other road users. Trucks within a certain radius connect to each other via WLAN in real-time, which is then further communicated to traffic lights and signs as they approach an intersection. If the road is clear, the traffic light can turn green. The model project is scheduled to run to the end of 2020.


In Vienna, following two years of testing, intelligent traffic lights have been gradually replacing around 200 existing push-button traffic lights in the city. The lights are embedded with cameras that detect people and whether they want to cross the road.

The city is also working to interconnect all traffic lights, enabling them to communicate with each other and resolve unpredictable traffic jams caused by accidents or construction sites quicker. Also planned is a collaboration with the Central Institute for Meteorology and Geodynamics (ZAMG), to equip traffic lights with 10,000 weather and environmental sensors. The data creates the ability to identify heat islands and identify air pollutants as well as track noise - all important components of smart city planning.

Emergency vehicles

Traffic lights in German city Ludwigsburg were recently fitted with Road-Side Units, which correspond with the equivalent On-Board Units in fire trucks and rescue vehicles to grant them green-light passage en route to emergencies, when every second counts. The system works by sending messages relaying position and speed, several times per second, from emergency vehicles to a traffic light controller. There, the signals are processed and compared with the scenarios stored in the programming. If the system detects an approaching emergency vehicle, the programmed signal sequence starts, and the traffic light controller switches to the prioritization program. Once the firefighters have passed the intersection, the traffic light controller switches back to normal as quickly as possible to minimize the impact on road traffic and traffic disturbance.

Smart buses

In Sweden, Skånetrafiken has launched the initiative Smart Prio to improve the traffic priority of buses. Previously, the most common solution giving traffic priority to buses was using radio beacons that send signals to traffic lights. This type of solution requires specialized hardware and regular maintenance. It is also a blunt tool for traffic priority, as little information is made available regarding the individual bus.

Collaborative work by Skånetrafiken, Swarco, Telia, and the city of Malmö, has finessed the technology so that traffic lights can prioritize a specific bus, based on which line the bus is driving and whether it is on time or not. No extra hardware is required as the solution uses data that is already generated by existing systems. Buses can also communicate their position, number of passengers, and any delays to the traffic signals and will be given longer green lights when they are behind schedule or full of passengers.


In the Netherlands, proof of concept trials have been carried out to prioritize green lights when bike riders approach. An example is the use of the mobile app Schwung. Once activated it connects the rider to smart traffic lights. The app starts automatically upon cycling (no action needed by the rider), and traffic lights identify that you are approaching and turn green. Smart lights for cyclists were recently criticized for security vulnerabilities. Hackers at DEFCON 2020 demonstrated their ability to turn them green without approaching on a bike, which is annoying rather than dangerous for the more comprehensive road users, but highlights the need for a security-first approach to design and testing further implementation.