Smart traffic lights: understand what they are and how they reduce traffic

The enormous time that is lost in traffic is one of the main problems of those who live in large urban centers, so there is a large investment in solutions to improve mobility. An example of this are the smart traffic lights, which have already been implemented at 1,677 intersections in the city of São Paulo and, according to the City Hall, contributed to reducing by 12.16% the slowness rates in the regions served, in addition to increasing the capacity of vehicle circulation by 5.72%.

Other cities such as Curitiba and, soon, Belo Horizonte, also have this technology, which is capable of benefiting drivers, cyclists and pedestrians. In this article you understand what a smart traffic light is, how it works and what is the impact in practice for urban traffic.

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What are smart traffic lights?

The smart traffic light is a set of equipment and software that controls the signaling of an intersection or a network of intersections with the ability to adapt. The adaptive traffic light system is a technology developed to manage road traffic dynamically and on demand.

Unlike conventional models, which work with pre-programmed timetables and times, smart traffic lights automatically adjust the opening and closing time of signals in real time, varying according to the number of vehicles and pedestrians in the area. The main objective is to optimize urban circulation, reduce queues and congestion, avoid unnecessary stops and provide faster and more predictable travel, benefiting drivers, cyclists and pedestrians.

How do they work?

The set of devices and software uses traffic data to define interleave times between green, yellow and red lights, in addition to coordinating the “green wave” in entire corridors. The central difference is not just “having a camera”. It is having a control model that reacts to real flow variations and that talks to other traffic lights or to a central station.

This technology can have different levels:

• Simple – traffic light acts on demand with sensors that detect vehicles or pedestrians and release phases when it makes sense.
• Intermediate – there is coordination by corridor, with dynamic adjustments of cycle, lag and time distribution.
• Advanced – adaptive algorithms come into play and, in some cases, artificial intelligence with prediction of arrival of vehicle platoons, as well as decentralized intersection-by-intersection decisions.

In general, the operation of smart traffic lights involves the following factors:

• Real-time data collection: cameras and sensors installed at strategic points at intersections continuously measure the number and volume of vehicles in circulation.
• Information processing: a system converts the images and captures from the sensors into real-time data.
• Automated adjustment by algorithms: through artificial intelligence and algorithms (such as the SCATS system, used in São Paulo), the system automatically calculates and changes traffic light cycles and stages.
• On-demand prioritization: if one lane at an intersection is more overloaded than the others, it will receive a longer green light time to relieve traffic.
• Synchronization by sub-area: the intersection with the highest traffic demand determines the traffic light cycle of its entire sub-area, and the system replicates these adjustments for the other traffic light sets in the region.
• Safety at pedestrian crossing: the crossing time for pedestrians is kept fixed, ensuring the safety of those who walk without suffering changes caused by the volume of cars.
• Application of the “Green Wave”: the system makes it possible to program traffic lights in open sequence to allow the passage of as many vehicles as possible without interruption. This feature requires that the road be one-way and present uniform characteristics of flow and land use.

Differences Between Smart and Traditional Traffic Lights

• Flexibility X Fixed schedule: conventional traffic lights operate based on rigid timetables according to the day of the week or time (such as night periods or peak hours), without adapting to atypical variations in demand. Smart traffic lights, on the other hand, continuously self-regulate throughout the day.
• Infrastructure and maintenance: traditional models use sensors affixed to the asphalt, which are usually damaged by resurfacing works or repairs on the road.
• Centralized monitoring and intervention: the intelligent system is integrated with monitoring centers and monitored in real time by operational teams, such as the Traffic Engineering Company (CET). This allows for rapid detection of failures that enable quick maintenance and remote management of unforeseen events by human operators such as accidents, demonstrations or road closures.

Impact of smart traffic lights in São Paulo

According to the City of São Paulo, the benefits of the technology were observed in all macro-regions evaluated by the Traffic Engineering Company (CET). The best results occurred in the Southeast and East zones, where circulation capacity increased 12.05% and slowness fell 26.04%.

In some road corridors, the numbers were even more expressive.

• Avenida Indianópolis – slowness decreased 66.2%, while the flow of vehicles grew 5%.
• Paes de Barros Avenue – reduction of congestion reached 57.1%, followed by an increase of 16.7% in the circulation of vehicles.
• Rua dos Trilhos (50%), Avenida dos Bandeirantes (29%) and Avenida Salim Farah Maluf (22.6%) also showed reductions in queues.

According to the City Hall, another 217 are in the final stages of implementation and 689 had their executive projects approved. The goal is to reach 2,583 smart intersections throughout the city. The planned investment is R$ 725.5 million. The largest concentration of technology is currently in the areas of the sub-prefectures of Sé, Vila Mariana, Pinheiros, Lapa, Ipiranga, Mooca and Santo Amaro.